Revised Origin of Cold Talus Habitats in the Columbia River Gorge and Implications for Dependent Species

Low-elevation talus slopes of the western Columbia River Gorge appear to be geographies that can sustain cold and possibly permafrost conditions usually found at either higher elevations or more northerly latitudes.  The formation of likely sporadic permafrost is due the unusual thermal behavior of blocky-rock deposits that cause them to lose heat in winter at a higher rate than heat can be regained during summer.  As a notable result, these cold geologies / habitats support populations of cool-loving and stenothermal animals including American pika and members of the Grylloblatta insect genus.  It is furthermore possible that the process has resulted in significant deposits of underground ice, which may constitute unknown water supplies important to human economies and aquatic life in the Gorge.

As highlighted in Ice Mountain —  A Theory of Why Pikas Exist in the Columbia River Gorge, the situation in the Gorge is not unique, as there are other geologies across the globe that display the formation of cold talus and potentially permafrost in areas that have annual average air and soil temperatures that are well above 0°C (32°F).  Based on extensive work to describe the phenomena at places like Creux-du-Van in the Jura Mountains of Switzerland, scientists have theorized that the creation of localized sporadic permafrost is a result of the “chimney effect” thermodynamic process.  But before examining that term, and whether it adequately explains the processes occurring in our talus slopes, a quick look at the term “permafrost” is warranted.

Permafrost

Permafrost is simply defined as a patch of the earth’s regolith that is frozen, and has been frozen for at least two consecutive years.  And to be clear, regolith is defined as the layer of unconsolidated rocky material including soil between the earth’s bedrock and its atmosphere or waters.

There are four main permafrost zones on earth:  a) zone of sub-sea permafrost; b) zone of continuous land permafrost; c) zone of discontinuous land permafrost; and d) zone of alpine land permafrost.   These delineations are shown on the below map taken from Pewe’s “Alpine  Permafrost in the Contiguous United States:  A Review”.   Cross hatched areas represent the zone of continuous permafrost, hatched areas represent discontinuous permafrost, and solid black color represents alpine permafrost.  The continuous and discontinuous permafrost zones occur well north of the states of Oregon and Washington, generally above 50° north latitude.  While frozen soil in these zones is generally dictated by proximity to the North Pole, alpine permafrost can form much further south, if at increasingly higher elevations.  These areas are mapped in Figure 1, and several patches of alpine permafrost can be seen in our area (i.e., near 45° north latitude) corresponding to Mt. Rainier, Mt. Adams, Mt. St. Helens and Mt. Hood.  It is generally assumed that permafrost in all three zones can only form in places where either high latitudes or elevations result in annual average temperatures of −2°C (28.4°F) or colder.

Figure 1.  Pewe’s map of permafrost distribution across North America.  See above paragraph for legend shading definitions. 

But not all patches of perennially frozen ground on earth are found in the zones pictured above, which are all proximate to the poles or at high elevations.  These outliers are lumped together into a fifth category, called sporadic permafrost, and occur on the equatorial sides of the earth’s bands of discontinuous permafrost, or locally below the elevations of alpine permafrost.

Formation of Sporadic Permafrost in the Gorge

The existence of currently active (as opposed to relict) sporadic frozen patches in areas with annual average temperatures above −2°C must be explained in all cases by mechanisms that cause a relatively higher loss of heat (i.e., cooling) from the blocky-rock feature to ambient environment in winter, than is gained back from the surrounding ambient environment (i.e., warming) in summer.  Perpetuation of even very small seasonal net losses over time can, therefore, result in landform temperatures that are well below annual average ambient temperatures, and even below freezing.  For these mechanisms to operate, however, there must be avenues for free air passage into the soil/rock mantle.  Indeed, I would predict it impossible for sporadic permafrost to develop in fine or mixed grained soils, or solid rock landforms.

To understand how this seasonal thermodynamic imbalance can arise in either cave or blocky-rock landforms, it is useful to remember a very simple maxim which applies to wintertime overcooling:  “hot air rises vertically as a gas, while cold air flows downward as a liquid”.  Both of these represent very efficient heat transfer processes occurring in winter.

Case 1.  The Ice Cave and other Topographically-Contained Landform Features

The simplest illustration of this maxim is what has been called the “Balch effect”, a process that operates in the case of a confined, downward-inclined earth opening.  This situation was perhaps first described by Edwin Swift Balch in his 1900 book titled Glacières, and is best exemplified in our area by the Trout Lake and associated Big Lava Bed lava cave systems.  During the coldest periods of winter (dominated by stable high pressure systems, clear nights and little regional winds), very cold layers of air exist at the land’s surface.  Once formed, this dense, stable, heavy air behaves as a liquid, and flows down-slope in a very non-turbulent manner perpendicular to landscape contours.  When this cold layer encounters any depressions in the earth surface (whether a broad open basin, confined cave, blocky-rock deposit, etc.), it flows in and displaces any air that is even minimally warmer, less dense, and therefore more buoyant.  This obviously causes the upward displacement of any warmer air occupying the depression, resulting in a temperature inversion (i.e., a layer of cold air trapped next to or within the ground).

Topographically-depressed reservoirs of cold inverted air may or may not be stable depending on the ambient surroundings and the nature of containment.  Inverted air masses, in general, are extremely stable as long as they remain “capped” and isolated from outside heating influences, whether caused by the rising of warm air (thermal cell convection), advection due to regional winds, direct conduction from the earth or atmosphere, solar radiation, air pumping due to barometric pressure changes, etc.  Taking the example of cold air trapped in a desert basin, the stable inversion can be rapidly “uncapped” during mornings by solar heating of the basin’s surface, which in-turn results in upward rising convection cells, mixing, and warming of the once stable and overly-cooled lower atmosphere.

The absence of such “uncapping” mechanisms in the case of the protected ice cave perpetuates the existence of inverted conditions and the reservoir of cold interior air.  Once emplaced during the coldest periods of winter, the stable layer can persist throughout the summer season, aided by the large thermal mass of bedrock, lack of solar inputs, minimal downward conduction of heat from the surface, and absence of upward mixing convection.   The same thing can be occur in other depressed landscapes with openings, including topographically-contained blocky-rock deposits.

Case 2.  The Talus Slope and other Topographically-Uncontained (Sloping) Landform Features

It is more difficult to explain how a similar imbalance might occur in sloping blocky-rock geologies, including talus slopes.  Such geologies are the second landform type seeming capable of forming cold temperatures and potentially sporadic permafrost at low elevations in the Gorge.  The cause of the winter vs summer heating imbalance in such landforms is more complex than in the ice cave, given the vast numbers of multi-level air openings.  The deposits are also generally sloping and uncontained, therefore, seemingly prone to rapid gravity discharge of cold and dense air (and excessive warming) during summer.

Chimney effect diagram

Figure 2.  Conventional “chimney effect” diagram from the Sébastien Morard, Reynald Delaloye, and Christophe Lambiel 2010 article in Geographica Helvetica titled “Pluriannual thermal behaviour of low elevation cold talus slopes in western Switzerland”.

A currently accepted explanation for the formation of “cold talus” and likely permafrost at the base of some blocky slopes is known as the “chimney effect”, explained in the earlier article Ice Mountain:  A Theory of Why Pikas Exist in the Columbia River Gorge.   In short, the chimney effect results in differential heating and cooling of the blocky-rock slope, driven by seasonal differences in temperatures inside vs outside the deposit (see Figure 2 above).  As a result of these temperature and therefore density differences, the theory predicts that relatively warm subsurface air “chimneys” up-contour to the top of the slope in winter, thus forcing the simultaneous suction of cold stable air into the base of the slope.  This action can result in the formation of unusual open tunnels where heated air is output from the top of the snow covered slope.  The rate of cold air inhalation is directly related to the temperature and density differential, thus the velocity and volume of air intake is highest when outside temperatures are coldest.  In summer, air flow direction is reversed, when cold air sinks and flow back out of the bottom of the slope due to its relatively higher density than the outside air.  As this occurs, an equal volume of warm air is presumably inhaled into the upper slope.  This is thought to result in winter overcooling, and perpetually cold conditions inside the lower base of the blocky-rock slope.

There is no question whether chimney action causes seasonal transfers of air and heat wherever there are underground spaces with multi-level openings (e.g., talus slopes, some cave networks, etc.).  On its own, however, the usual chimney effect description doesn’t seem to explain why the total slope heat loss during winter is higher than total slope heat gain in summer.  Superficially, it would appear that the heat content of cold air being drawn into the uncontained slope’s base in winter should equal the amount lost by the discharge of cold air from the base in summer.  However, as in the case of ice caves, blocky-rock slopes display heat gain/loss imbalances that can result in perpetual cold talus and permafrost.  The following two sections will attempt to describe how this might occur.

Local Observational Evidence

Two side-by-side thermodynamic processes appear to drive the very efficient loss of heat from uncontained, blocky-rock landforms during winter, both understood using the simple maxim “warm air rises up as a gas, while cold air sinks down as a fluid”.

The long-wave infrared (LWIR) images below illustrate recently observed surface temperature effects present on talus during both the summer heating and winter cooling seasons.  Both frames show the northwest facing flank of Shellrock Mountain, Oregon, lying near sea-level just south of the Columbia River in the western Gorge.

The following observations related to summer heating period are made after examination of Figure 3.  First, the drainage of dense cold air (blue color) from the slope is immediately apparent along the lower margins of the talus skirt.  (It is hidden below the slope transect on this image due to tree canopy interference).  Second, above the cold air vent, there is almost no overall bottom-to-top trend in summer surface temperature along the slope transect.  Third, there is little variability in slope temperatures, resulting in a fairly smooth temperature graph that lacks spiky bumps and dips.  Surface temperatures are limited within a narrow 1.7°C range.

     

Different observations are apparent during the winter cooling period, as illustrated in Figure 4.  First, and as expected, the drainage of cold air from the bottom of the slope is absent due to internal temperatures now being above outside temperatures.  Second, as also seen in summer, there is little overall trend in surface temperatures from bottom-to-top of the slope transect.  Third, winter surface temperature variability across the transect is high, as evidenced by the graph below the image that ranges between 3.9 and 7.0°C  (3.1°C range).  This observation is best realized when viewing the very spiky nature of the temperature graph.  Finally, the image does not show indication of the presence of large patchy warm air vents on upper portions of the unbroken talus plane.   This supports the contention that warm air is not being conveyed upslope and within the blocky-rock mass, as the chimney effect theory predicts.  While large warm air vents are present on the left side of the Figure 4 image, these vertically-elongated winter features are clustered at the bottom and middle portions of the talus mass, and not at the top of the slope.  The large vents shown occur at topographically-uneven faces of the slope, characterized by convex ridges and concave rills associated with past slope movements.  They are not, therefore, considered relevant to consideration of the chimney effect, or the theory currently offered.

The above observational evidence indicates that significant winter overcooling is being driven by the formation of a multitude of small vertically-rising convection cells originating within the talus, which occur across the entire breadth of the unbroken talus field.  The vertically-rising convection cells are indicated by the individual spikes seen along the winter fall-line transect graph.  Each spike likely represents a column of rising warm air that is very efficiently conveying heated air vertically-upward and out of the slope. By my calculation (and pending possibly unknown limitations of the LWIR camera’s resolution), the average on-ground distance between the presumed convection cells equals 16 feet.  This equates to a density of 170 convection cells per acre.

The winter image also hints that the vertically-rising convective heat transfers are coupled to vertically-downward fluid-like intakes of cold and dense winter air into the landform between convection cells.  These induction areas are likely indicated by the troughs seen on the graph.  The high cooling efficiency of this arrangement somewhat assumes that the closely proximate upward and downward trending air parcels do not significantly intermix either underground or above the surface.  During cold and calm winter weather  patterns, it may be possible that the convection cells persist in a confined upward direction well after they emerge from the talus surface, thus allowing the proximate downwelling of dense cold air with little intermixing.  If this is the case, the effect may be identical to the up-and-down convective movements of air parcels during thunderstorms, where there is little intermixing.

Assuming the above two linked mechanisms drive the primary winter cooling process, it is not likely that significant amounts of cold air are being inducted into the base of the slope, as the chimney effect model predicts.  Instead, it appears that the entire blocky-rock deposit is being cooled from surface to base, as one uniform mass, during winter.  If bottom-of-slope intake does happen, it would probably only be forced when a continuous blanket of snow is present, creating a closed conduit for the warm and low-density air being buoyed upward.

It is also necessary to touch upon why summer heating mechanisms are comparatively weaker than the cooling mechanisms of winter.  This is fairly easy to understand in the relatively simple case of the ice cave.  Once warm air is displaced by the down-gradient flow of cold air into the contained and “capped” underground cavity, the cold inverted air is very stable in temperature and volume.  In a relatively small cave, the only means of introducing summer heat and uncapping of the inversion would be via the very inefficient downward conduction of ambient heat from above.

The inefficiency of summer heating in a sloping blocky-rock landform such as a talus slope is, however, more difficult to explain than in the contained ice cave example.  The difficulty stems from the fact that talus deposits are inclined and lack the bowl-like topographic containment of an ice cave; therefore, any cold air reservoirs forming in winter above the bedrock surface would tend to flow out of the slope’s base in summer.  While this unquestionably occurs (see evidence of lower-slope cold venting in Figure 3), the fact that this does not result in a high degree of summer heating is likely because the sub-surface flow of the inverted air mass is greatly slowed by physical resistance within the porous talus.  This resistance is compounded by the long distance the cold subsurface air must follow from top to bottom of the talus slope interior.  The inverted air mass contained in the base of a cold talus slope, therefore, might be comparable to a perennial lake having a restricted overflow/outlet channel, which due to its configuration lacks the ability to rapidly drain, and is thus fairly stable in volume.

Finally, note that this same internal resistance is likely responsible for the earlier hypothesized low rate of inhalation of cold air into the base of the slope in winter.  It is presumably much more efficient that the intake of cold air occurs vertically and downward, and immediately proximate to the multitude of vertically-acting warm air convection cells.  A vertically downward pathway for winter air intake is logically the shortest, least resistant, and most efficient pathway.

Applied Engineering Evidence

Civil engineers working in northerly latitudes have long recognized that roads, pipelines and other structures built upon relatively warm permafrost are subject to failure upon melting of the permafrost layer and deflation of the local landscape surface.  Melting is a consequence of replacing native soil and vegetation layers with non-porous compacted earth and pavement, and therefore, loss of the temperature buffering and cooling mechanisms important to maintaining the permafrost layer.

To counteract the loss of permafrost after construction, D.J. Goering at the University of Alaska Fairbanks has experimented with systems known as air convection embankments for protecting roadways and other structures built on warm permafrost.  Such systems involve perching structures atop a layer of porous gravel or rock having low fines content and narrow particle size gradation.  In the beginning, such construction may have been believed simply a means of insulating the frozen ground surface from the summer’s heat.  Eventually, however, Goering came to realize that a passive refrigeration effect was largely responsible for maintaining frozen ground conditions in the underlying soil layers.

To understand the apparently passive cooling mechanism, Goering built an experimental eight-foot thick, unconfined porous rock embankment near Fairbanks, and laced it with electronic temperature probes placed in a three-dimensional grid pattern.  After monitoring the internal and external temperatures for two years, and then modelling the internal heat flows, he was able to decipher how ground temperatures at the base of the embankment were being maintained below freezing.  The experimental findings closely match the LWIR imagery observations and the ideas presented in the last section of this article.

The following quote from the 2003 paper titled Thermal response of air convection embankments to ambient temperature fluctuations, effectively summarizes Goering’s findings:

“During the winter, the embankment is cooled at its upper surface due to low ambient air temperatures.  If the cooling is strong enough and the embankment material is of sufficient permeability, natural convection of the pore air will occur during winter months due to the unstable pore-air density gradient that develops.  The convection can transfer heat upward out of the embankment at a rate that may be more than an order of magnitude larger than conductive heat transfer, resulting in greatly enhanced winter cooling.  During summer the pore-air density gradient is stable and convection does not occur. Thus the embankment acts as a one-way heat transfer device or thermal diode that effectively removes heat from the embankment and underlying foundation material during winter without re-injecting heat during subsequent summers”.

Diagrams showing the isotherm lines and convection cell boundaries discovered by Goering illustrate the internal processes likely responsible for over-cooling the interior of Columbia River Gorge talus slopes.  These diagrams are presented below as Figures 5 and 6.  The non-spiky summer surface temperatures earlier shown in Figure 3 are explained by the stable and laminar sub-surface thermal patterns depicted in the experimental embankment shown in Figure 5 below.  Likewise, the more spiky surface temperature range seen during winter in Figure 4 is explained by the formation of the vertically-oriented internal convection cells seen in Figure 6.

     

Conclusions

Recent results of the Shellrock Mountain LWIR imagery work, combined with experimental evidence reported by Goering in 2003, support the conclusion that vertically-oriented, cell-confined “pore air convection”, and proximate subduction of cold and dense winter air is responsible for the existence of cold and sometime frozen ground in open, blocky-rock deposits of the Columbia River Gorge.  Very significant temperature declines can occur within blocky-rock slopes and embankments within a period of a few days or even hours during cold periods. These rapid events represent periods of intensely non-linear cooling, and have a disproportionally large impact on ground temperatures when averaged over the year.  The experimental evidence also indicates that gravity-driven outflow of cold air from a slope or embankment base in summer is a relatively inefficient means of landform warming, which does not necessary result in the melting of permafrost.  Even lacking the topographic containment of an ice cave, the inverted cold air mass remains relatively stable within the sloping blocky-rock deposit during summer.  This is probably due to high internal resistance to summer gravity-driven outflow of the stable inverted air system, as it flows downward along the long talus slope / bedrock interface.

Given the likelihood that pore air convection is the main mechanism responsible for winter over-cooling and sporadic permafrost formation within sloping blocky-rock deposits, I suspect that the winter-time chimney effect can be viewed as an inefficient manifestation of pore air convection occurring under snow layers.  In such circumstance, the very efficient co-existence of upward trending warm air convection cells with side-by-side cold air downwelling is interrupted by the snow layer.  As warm air rises within the blocky-rock deposit and nears the rock / snow interface, it is forced to follow an upslope path through the porous rock just below the snow surface.  Perhaps more important is the fact that the volume of warm air displaced upward is not being directly replaced by cold downwelling air from the open atmosphere.   Instead, rising warm air trapped below the snow layer causes a slow suction of cold air into the slope via transfers through the snow layer, and into the base of the slope.  The resulting mixture of inside / outside air then moves upward below the snow / rock interface at a relatively low velocity.  The rate of winter slope cooling is, therefore, significantly retarded by a) the low volumes of cold and warm air that can transfer through the snow cover, b) the high flow resistance encountered by rising air being sucked upward within the porous rock deposit, and c) the fact that the external cold air and internal warm air are being constantly mixed within the porous slope just below the snow layer.

The above conclusions indicate that the creation of sporadic permafrost and periglacial landforms is most likely to occur in zones characterized by low snowfall accumulation and periods of cold winter temperature.   Such conditions were at a maximum in the late Pleistocene, some 16,000 to 20,000 years ago throughout the Columbia Basin of the Pacific Northwest.  During that time, climates were dominated by cold and dry continental air masses (high pressure systems), that blocked entry of wet maritime weather systems onto the continent.  There is also evidence that lesser such conditions existed into the Holocene period, and may be still present today, evidenced by sporadic permafrost scattered across the Pacific Northwest.  In the case of the western Columbia River Gorge, the occurrence of scattered permafrost can be partially attributed to the fact that the region exhibits large masses of porous talus occurring in low-elevation snow-free zones, which is favorable to efficient pore air convection.  Equally important, however, is the fact that dry and cold continental weather patterns are still very dominant aspects of our winter weather.  Each winter, we experience periods when calm and cold air settles into the Gorge from the east, resulting in prolonged periods of sub-freezing temperature.  These periods, which Goering has shown to have the ability to cause intensely non-linear cooling of blocky-rock deposits, must largely account for the occurrence of our cold and likely frozen blocky-rock slopes.

Finally, the apparent overwhelming dominance of non-linear winter cooling within blocky-rock landforms indicates that long-term plant and animal habitat temperature trends are not simply dictated by annual ambient temperatures, or even by annual high temperatures.  It is therefore impossible to conclude that simple rises in regional or global average temperatures can be directly correlated to an increased threat to populations of stenothermal talus or cave dwellers.  Instead, experimental findings reported in this article indicate that the long-term thermal stability of blocky-rock habitats is dictated by the number and length of periods when temperatures drop below specific levels.  This, of course, greatly complicates any attempt of forecasting long-term population trends or threats of species declines for organisms dependent upon such geological habitats.  This is not to say that such threat analysis is impossible for rock and cave dwelling organisms such as pikas and grylloblattids, but only that conclusive answers will likely depend upon multi-disciplinary efforts involving geologists, meteorologists, climate scientists, statisticians, biologists and physicists committed to the work.

Steve Stampfli

21 May 2019 at White Salmon, Washington

– END –

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Stronghold of the Ice Crawler

The occurrence of currently active geologic and weather processes that result in formation of both summer cold and winter warm temperature geological zones (and biological habitats) in Shellrock Mountain talus slopes is certain.   But in addition to that, it now appears possible that a second western Columbia River Gorge area could harbor several acres of relict periglacial terrain that dates back many thousands of years.  That seemingly bold statement is supported by growing biogeographic evidence.

Evidence of the second periglacial area arose via a March 6, 2018 email from biologist Jim Kirk, who had recently read the first article in the GorgeScienceShare blog “Ice Mountain – A Theory of Why Pikas Exist in the Columbia River Gorge”.   Kirk is an experienced field biologist who worked during the early 1980s describing the distribution of plethodontid salamanders in the western Gorge.  His email concluded with the amazing statement that he had trapped grylloblattid insects (ice crawlers) just above the Columbia River and west of Shellrock Mountain in February 1983… some 36 years ago.

It appeared that Kirk had discovered one of nature’s rarest and elusive insects.  But even more remarkable was the fact that the discovery was made far from their typical mountain, snowfield and glacial haunts, at an almost sea-level elevation in the western Columbia River Gorge.

Figure 1.  Recently molted immature ice crawler (Grylloblatta) from a lava tube cave near Mt. St. Helens in the state of Washington (photo courtesy of Joe Warfel).

~ The Ice Crawler ~

Ice crawlers are members of one of the world’s oldest insect orders, Notoptera, which date back 200 -250 million years to the Permian period of the late Paleozoic era.   When Notoptera first appear in the fossil record, the earth’s climate was typified by high carbon dioxide levels, and much warmer temperatures than today.  It was also a time when a huge amount of forest vegetation was being produced, and its carbon photosynthetically fixed and geologically sequestered.

The fossil record shows that early members of the order had two pairs of large wings that enabled them to travel widely throughout the hot and tropical forests, feeding on pollens from early conifers and other early plant types.  They filled a pollinator role in the primordial forests, much in the same role as today’s bees and wasps.  But then, a series of changes in the earth’s climate and biology occurred that would change the planet’s evolutionary path forever… the advent of flowering plants.

As Harvard biogeographer, writer and photographer Piotr Naskrecki wrote in his 2010 “The Smaller Majority” blog, “gradually, they (ice crawlers) disappeared from the fossil record. Strangely, there is not a single ice crawler known from the period after mid-Cretaceous. Their disappearance coincides roughly with the appearance of flowering plants, or angiosperms, and the nearly concurrent diversification of beetles and other plant pollinators. It seems that rather than allowing themselves to be outcompeted by this new army of more advanced plant-associated insects, the ancestors of ice crawlers found survival in a completely new lifestyle”.

Instead of being forced into extinction by the myriad new insect forms tailored to angiosperms, the ice crawler’s ancestors took advantage of previously unoccupied habitats that were forming on the then cooling earth.  These habitats amounted to the periglacial environments forming around the margins of glaciers and snowfields, plus the interior of frozen rock fields and icy caves.  In adapting to these cold and largely subterranean environs, the early Notoptera shed their wings and adopted a lifestyle based upon hunting other insects, and scavenging what food was carried into their range by wind and gravity.  Rapid decomposition and lack of inundation by fine particles in their new rock and snow haunts was not conducive to fossilization of their remains, hence the seeming disappearance of grylloblattids from the fossil record.

Today’s Grylloblattidae are a rare family of insects restricted to cold mountainous areas in western North America, and parts of northeastern Asia including Japan, both Koreas, China, far eastern Russia and south central Siberia.  As of 2018, the family exhibited just 33 species and 4 subspecies, within 5 genera worldwide. It belongs to the second-smallest insect order, Notoptera, along with the family Mantophasmatidae (rock crawlers).  All grylloblattid species are highly endemic, thus have very small geographic ranges (i.e., a median geographic area of only 179 square kilometers, or 79 square miles).  In North America, there are now 15 documented species and 3 subspecies, plus a number awaiting verification via physical and genetic analysis. North American distribution is limited to the states of Washington, Idaho, Montana, Oregon and California, and the provinces of Alberta and British Columbia.  (Note:  much of the technical information on grylloblattids presented in this article is from Schoville and Graening, 2013. “Updated checklist of the ice-crawlers of North America, with notes on their natural history, biogeography and conservation”).

The chief reason ice crawlers display such small endemic ranges and have such poor dispersal abilities is their evolutionary adaption to very narrow habitat temperatures (i.e., stenothermalism).  Almost all ice crawlers are found in habitats with rocky retreats that maintain steady cool temperatures and humidities throughout the year.  Fifty years ago, a pioneering grylloblattid researcher named Bill Kamp recognized that the cryophilic (i.e., “cold loving”) nature of the genus Grylloblatta along with its unusual distribution correlated with Pleistocene glacial advances.  He proposed that surviving populations would be limited to areas that were previously glaciated or at the edge of glaciers (i.e., periglacial environments) since the last glacial maximum some 21,500 years ago.  Ice crawlers are normally active above-ground during the night, but only when temperatures hover around freezing.  They show a preferred temperature range of 0-1° C.  The range associated with an undescribed species on Mt. Rainier, for example, shows acute temperature thresholds between -8.5 and 15° C.   This supports the colorful statement that human touch can transmit enough heat energy to kill the insects.

~ The Stronghold ~

Jim Kirk’s announcement of his 36 year old discovery was notable from the biogeography standpoint, since it was signal of yet another cryophilic and stenothermal organism being harbored in the taluses of the western Gorge.  Proving the continued presence of the organism would also support the odd probability presented in the first article that low-elevation permafrost conditions still exist hidden in the Gorge.

With a little research, I soon determined that there are several prominent entomologists in North America and northeast Asia who specialize in the study of ice crawlers, and who may be interested in understanding the significance of the animal’s occurrence in the Gorge.  One of these is Dr. Sean Schoville of the University of Wisconsin Department Of Entomology, who further specializes in the tools of molecular ecology.  Molecular ecology is the exciting, relatively new field that utilizes DNA analysis to unlock how new species evolved on our planet, and how they fit into the modern-day ecological framework.  Just as any of us are now able to use emerging genetics labs to uncover our own human history, scientists like Schoville use similar sequencing equipment to analyze insect DNA for understanding species evolution and ecologies.   (See https://www.biographic.com/posts/sto/bugs-on-ice for a well-written description of ice crawlers and the folks who study them).  Other prominent ice crawler researchers are located right here in Pacific Northwest, in the persons of Dr. Chris Marshall and Dr. Dave Lytle, both entomologists in Oregon State University’s Department of Integrative Biology.  This team recently uncovered two new grylloblattid species in the mountains of Oregon, including the snowfields around Mt. Hood (see this OPB Oregon Field Guide video segment .

After contacting Sean, Chris and Dave with details of my own work, and the report of Jim Kirk’s original discovery, all three agreed to help sleuth whether ice crawlers were indeed harbored in the Gorge, and if so what species are present and how they fit into the broader North American distribution.  In addition to these three, others who agreed to provide advice during the project included Jim Kirk, Dr. Scott Hotaling of Washington State University School of Biological Sciences, and Dr. Jeff Holmquist of UCLA Institute of the Environment and Sustainability.  The US Forest Service also agreed to become a partner via issuing a special use permit for grylloblattid collection activities, effective September 2018.

The very first visit to the site’s on-ground coordinates supported expectations of what I would find.  Most of the north-facing slope was dominated by well-sorted talus that was relatively free of fine-grained rock and soil particles.  Such “open” talus slope conditions seem prerequisite to free air exchange, and active slope cooling / warming mechanisms that can result in temperature-moderated habitats (see Ice Mountain article for description of Balch and chimney effects).  Infrared imaging currently being used at Shellrock Mountain is indicating that summer surface temperatures at the bottom of certain talus slopes are approximately 10° C cooler than temperatures slightly upslope.  Similarly during winter, mid-slope warm vents areas are being shown to have temperatures about 5° C warmer than nearby cold zones. The existence of habitats that display cold and hot zones in close proximity could be vital to organisms like ice crawlers, which are physiologically limited by both hot and cold extremes in summer and winter.  Importantly, LWIR imagery is showing that talus hot and cold zones can be only tens-of-feet of one another, therefore seasonally traversable by organisms with limited migrational ability.

But beyond the talus substrate, I noticed something related to the topography that I’d never seen before.  Kirk’s original trapping site and the surrounding thirty acres had somehow been shaped into a series of five, symmetrical east-west trending ridges and trenches.  The appearance was reminiscent of the artificial earthen structures built as fortification around hillforts and castles during Europe’s prehistory and Middle Ages (see Figure 2 and Figure 3 below).  If still present, Kirk’s anomalous low-elevation ice crawler population seemed to be harbored within a natural fortress comprised of a series of ramparts.  There was irony in the situation, since grylloblattids appeared to be taking refuge in a landform resembling the fortresses used by our own ancestors long ago for repelling invaders.  Of course, in the ice crawler’s case the refuge was likely providing stable temperatures in a larger world of much broader temperature extremes.  But that colorful wondering aside, the chief task for the moment was determining whether ice crawlers still occupied the site.

Figure 2.  Artificial earth ditch-and-rampart defenses from the Bronze Age at the Ipf Hill Fort, Bopfingen, Germany (from Dark Avenger at de.wikipedia ).

Figure 3.  Interior of 4th natural rampart at the “Stronghold” grylloblattid survey site, viewed from the east end (Stampfli photo).

The Columbia River Gorge grylloblattid survey was initiated on-ground in late October of 2018, and within one month the first ice crawler was trapped at the “Stronghold” study site.  This confirmed the validity of Jim Kirk’s historic observation, and happily signaled that this uniquely cryophilic (cold loving) and stenothermic (narrow temperature range) insect still inhabited the apparently ancient landform.

Sampling is on-going at the 30 acre site, plus some nearby talus slopes.  As of December 31, 2018, I had collected a total of 76 individuals for morphologic examination by Marshall and Lytle at OSU, and accession into the Oregon State Arthropod Collection.  Tissue samples for genetic analysis and species determination are also being forwarded by the OSU team to Schoville at the University of Wisconsin.  The western Gorge grylloblattid project is still in its early stages.  Therefore, the identification of what species are present is incomplete, as is understanding of the broader Gorge distribution and how Gorge species may relate to the higher elevation populations found on Mt. Hood, Mt. Adams vicinity, and elsewhere in the western US.

~ Periglacial Landforms in the Columbia River Gorge ~

There is no evidence that either continental ice sheets or Cascades Range alpine glacial conditions extended to low elevations in the western Columbia River Gorge during the height of the Pleistocene or later Holocene epoch.  The Laurentide ice sheet reached a point about 150 miles north of the western Gorge some 16,000 – 20,000 years ago, thus did not directly impact the area.  However, the massive ice sheet’s influence on western US climate, geology and natural history was enormous, given two primary factors.  First, the North American jet stream had become split, and the southern branch (and therefore the location of winter storm tracks) shifted south.  This southerly shift robbed the Pacific Northwest of its marine-derived moisture and moderated temperatures.  Second, due to the anticyclonic (i.e., clockwise) direction of winds that prevailed over the ice sheet, easterly “continental” wind patterns accompanied by dryness and cold became dominant (see Kathy Whitlock’s 1992 paper entitled “Vegetational and Climatic History of the Pacific Northwest during the Last 20,000 Years: Implications for Understanding Present-day Biodiversity”).  As a result of these two factors, plus the already cooling global climate, processes that supported the formation of periglacial steppe environments and landforms became dominant in the Pacific Northwest interior at the end of the Pleistocene.  From the geomorphology standpoint, mechanical weathering processes such as the freeze-thaw responsible for the formation of fractured rock deposits and localized permafrost conditions would have become very active during this epoch and later glacial re- intensifications during the Holocene.

Perhaps the most obvious example of a once large-scale, likely inactive periglacial landform in the Gorge is found in the Catherine Creek area east of Bingen, Washington.   This location exhibits large areas of what has been termed “fractal patterned ground”, and also what I believe to be a dormant or fossil rock glacier.  This feature would have once transported rock in an icy matrix down to the Columbia River from the 1,000 foot elevation scarps to the north.  Similar large-scale, but now likely dormant or fossil periglacial features can be witnessed just across the river near Mosier, Oregon.  These mostly unstudied and poorly understood landforms will be the subject of a future blog article.

There are at least two examples of relict, likely active periglacial landforms in the western Columbia River Gorge.  Both of these occur within the 20 mile reach between Shellrock Mountain and Multnomah Falls.  Not surprisingly, this is also the reach that displays anomalous low-elevation populations of the cold-adapted and stenothermal American pikas and grylloblattid insects.  The first example is the Shellrock Mountain talus slope described in the Ice Mountain article.  The second likely active feature is the subject of this current writing.

Over the course of several visits to the Stronghold site, I tossed around various explanations for how the linear ridge-and-trench (rampart) topography could have come to exist.  The question was also posed to a few professional geologists for their interpretations. To enable better examination, it was apparent that having a broader “looking glass” via the use of lidar imagery would be helpful.  Thanks to assistance of Hood River County GIS Coordinator Mike Schrankel, the below lidar image was soon acquired.

Figure 4.  Lidar imagery of suspected Pleistocene and Holocene pro-nival ramparts, being overtaken by more recent alluvial, landslide and talus fans, west of Shellrock Mountain, Oregon.  These ramparts represent at least one of the landforms now known to support grylloblattid (ice crawler) populations in the western Columbia River Gorge.

The first of the eventually rejected explanations for formation of the landforms shown in Figure 4 is some type of bedrock-source movement, such as rock falls, rock avalanches and/or translational rock slides.  The source of material for all of these mechanisms would principally be mechanical weathering of the currently 800 foot tall head scarps (cliffs) uphill of the features.  Typically, as bedrock scarps mechanically erode, they gradually shed rock, and “march” backward and usually upslope (in this case, to the south and toward the bottom of the image).  This results in stable, tapering talus and debris fans, and not trenches and ridges.  This holds true in all climatic and geological environments I am aware of.  It is also true that such large-rock dominated fans display high internal friction, and are not prone to rotational debris slides (slump-type failures), which could theoretically result in irregular ridge-like features on receiving lower slopes.  Note that the rampart features are mostly composed of well-sorted talus, and not the very mixed materials observed at surrounding fans of alluvium and landslide debris, which conceivably could be prone to mass movement and irregular downslope deposition.

A second currently rejected explanation of the Stronghold’s ramparts is that they were formed by a common periglacial process known as thermokarst deflation.  Just as “sinks” or depressions are formed in limestone terrains due to the dissolution of soluble bedrock from below, depressions can also be formed in permafrost terrains via the melting of subsurface ice.  Elongated and concave (dish-shaped) thermokarst depressions can form at the base of frozen talus slopes, when their basal ice lenses disappear during persistent warm periods.  I have found likely examples of such thermokarst at the 4,000 foot elevation on the Washington side of the Columbia River.  While the Stronghold seems to exhibit characteristics favorable for the formation of permafrost and the accumulation of subsurface ice, it is not clear why a series of parallel thermokarst depressions would result upon thawing.

The third hypothesis that might explain the origin of the Stronghold’s talus ramparts relates to the series of glacial outburst floods that occurred at the end of the Pleistocene epoch some 13,000 to 15,000 years ago.  Although far-fetched, the hypothesis is interesting to consider, and could deserve more careful consideration by geologists.  Many travelers on I-84 westbound have noticed what looks like a westward trending side canyon on the south side of the interstate west of the Shellrock area.  This appears to be an ancient 3.8 mile long high-water passage “channel” formed during the floods.  The channel passage climbs 400 vertical feet to a crest of 570 feet before dropping back down to the Columbia River.  At least one of the flood events may have reached an elevation of some 750 feet in this reach of the Columbia, thus easily filling (and perhaps creating) this channel passage via massive river erosion.  Interestingly, this projected flood crest is at, or a little below, the elevation of the Stronghold ramparts.  It is therefore conceivable that large blocks of ice floated by the floods could have bulldozed deep gouges into the talus dominated shoreline, and resulted in the striated surface seen on the lidar image.  Although it is hard to flatly reject the possibility that ice age floods bulldozed the Gorge’s Pleistocene shorelines, it is unclear how such gouging action could have resulted in such a well-spaced series of relatively uniform gouges.

The fourth possible, and I think most likely explanation of the Stronghold terrain, is that it represents a series of relict periglacial landscape features known as pronival ramparts.  Such ramparts are simply ridges of moderately well-sorted talus debris that was originally shed from an overhanging headwall, landed atop a steep snowfield, rolled down the snow/ice slope, and was finally deposited at the base of the snowfield.  Sorted talus is a material that geologists typically see just below headwall sources, so the first clue to the rampart’s periglacial origin is its anomalous location well downslope of the main cliff pediments.  Pronival ramparts account for such anomalous location of graded talus given the fact that the snow field ramps act much like a combination “grizzly screen /conveyor belt”, which “screens”-out smaller particles as the mixed material works its way down the snow slope.  Eventually, only the larger rocks find their way to the base of the snow field for final deposit.  Rock sorting on snow slopes is therefore very similar to that occurring on an angle-of-repose receiving slope, where fine particles (the lesser volume, in this case) settle to the slope first, while larger diameters (the bulk of the volume) roll or slide to the bottom.  Here they can form rampart features in straight or arcuate ridges, well downslope of any cliff base talus accumulations.  Note, however, that rock-on-snow transport can occur at low gradients, and the eventual point of deposition can be anomalously far downslope.

Figure 5.  Genesis of a pronival rampart (from http://www.landforms.eu).

To enable formation of multiple and large pronival ramparts in the western Gorge, the presence of intermittent perennial snowfields would have been necessary, perhaps beginning in the late Pleistocene and ending as recently as the Little Ice Age (about 1900 AD).  The possibility is not hard to accept when realizing that deep depths of hard firn or ice pellets covered the Oregon side of the western Gorge as recently as the winter of 1884-85 (near the end of the Little Ice Age), and again 1922 (see discussion and historic snowbank photo in Chapter 4 of the Ice Mountain blog article).  It is logical to assume that even those recent and relatively small snow or ice fields could have lasted throughout following summers, given up to 20 foot depths of ice and the high degree of topographical shading on the Oregon side of the Columbia.

But what could explain the multiple parallel ramparts at the Stronghold site, instead of there being only one?  One idea is that the ramparts were deposited sequentially during the series of cold climatic periods that occurred in the late Pleistocene and Holocene.  As episodic cold periods favorable to mechanical freeze-thaw action ensued, the hard snow ramps necessary for rampart formation may have formed and lasted for decades or even centuries. They may have also been insulated from summer melting by veneers of insulating rock and soil, much as can be witnessed protecting the rock-veneered glaciers on Mt. Hood today.

It might, therefore, be reasonable to hypothesize that rampart formation corresponded to the major periods of cooling that began as early as 20,000 years ago, and ended as late as 1,900AD.  If glacial flood elevations did not rise above the lowest rampart (and thereby wash it away), it is conceivable that it was deposited during the first Cordilleran glacial maxima event (Evans Creek Stade) some 17,000 -22,000 years ago in the late Pleistocene.   Following this, a subsequent rampart could have formed during the second Cordilleran glacial maxima known as the Vashon Stade, some 14,000 – 14,500 years ago.  Following the end of the Pleistocene (and glacial floods), the Pacific Northwest entered a 3,000  year span of warming during the early-mid Holocene epoch (Holocene Climatic Optimum) between 6,000 and 9,000 years ago.  At the end of this warm period, the region experienced a new series of recent cooling periods that could correspond to subsequent rampart depositions.  A first Holocene “new glacial maxima” period occurred some 5,000 -6,000 years ago, which was followed by a second such period 2,500 – 3,500 years ago.  A third and final Holocene glacial maxima, known as the Little Ice Age, started in 1,350 AD and lasted until the current era of glacial retreat began in 1,900 AD.  That said, there seems no current way to determine ages of the five ramparts, and thereby sequence their formation.   Sequencing might be possible if a person had the ability to date the cliff and talus features in consideration of the past climates.

While the north and west slopes of Shellrock Mountain likely display currently active periglacial processes and permafrost, the Stronghold situation is less certain.  The strongest evidence in favor of permafrost at the site is biological, and the fact that the landform supports a population of insects that are believed to have dispersed along the advancing and receding margins of the Pleistocene continental ice sheet.  Additionally, these animals display physiologies that require current day habitats that never stray far from the freezing point.

Acquiring physical evidence of permafrost conditions within the Stronghold ramparts is in its early stages.  So far, fall-season LWIR imagery has indeed shown anomalously cold zones at the bottom of the trench features.  Additionally, the persistence of tiny interior patches of snow was noted during late fall 2018.  Both of these could be evidence of active Balch and chimney-effect processes.  Better knowledge will be available in the future, given the fact that sub-surface temperature loggers were installed in fall 2018 to track bi-hourly temperatures for the next several years.

Acknowledgments:

I thank Jim Kirk, Sean Schoville, Chris Marshall, Dave Lytle, Scott Hotaling and Jeff Holmquist for their considerable technical, curatorial, lab, and advisory work  related to this project.  I also thank Steve Castagnoli for providing use of the entomology lab at OSU’s Mid-Columbia Agricultural Research and Extension Center in Hood River, and Hood River County GIS Coordinator Mike Schrankel for producing lidar images .

Comments on this article can be posted below, or via email at stampfli@gorge.net.

Unseen Beauty: Early Evaluation of Using LWIR Thermography for Investigating Talus Properties and Relations to Pika Habitat at Shellrock Mountain

The first article in this series argued that American pikas living in hillside talus terrains are likely dependent upon steep, actively ventilated, blocky rock slopes that maintain moderated sub-surface temperatures via the chimney effect, at least in low-elevation regions like the Columbia River Gorge of Oregon and Washington.  Since that article, however, I’ve been a little stumped by how that theory might ever be proven. 

It initially seemed logical to use arrays of temperature loggers buried within Shellrock Mountain’s talus slopes to verify the location of active chimney effect talus processes, quantify slope temperature gradients, and pinpoint the location of hot and cold anomalies.  Given enough study locations, loggers and effort, it might have been possible to correlate these locations and their thermal character to mapped pika occupations.  Whether such a plan would have worked, however, is doubtful given the huge landscape scale.  The examination of a new and likely better alternative is the subject of this article. 

Overview

Shellrock Mountain sits about 10 miles west of Hood River, Oregon where the Columbia River has carved a deep gorge through the Cascade Range.  The lower Columbia River Gorge is unique, given the fact it supports a very low-elevation population of American pika, a typically montane or alpine species that likely exhibits narrow temperature tolerances. Does the very unusual sea-level presence of pika in the Gorge indicate that this population has undergone some physiological adaptation to the region’s physical environment, or is it possible that the species is simply making use of some unrecognized aspect of its talus habitat?

The purpose of the first article in this science blog was to introduce the June 2017 discovery of an anomalous cold (possibly frozen) patch of ground on Shellrock Mountain’s northwest slope, and very near the most easterly population of low-elevation Gorge pikas. The article went on to hypothesize that based on the discovery of this cold zone (i.e., “Big Cold Vent”), a little known thermal mechanism known as the “chimney effect” could be responsible for anomalously cold conditions, and maintaining the temperatures of sub-surface talus pockets (i.e., refuge) utilized by pika within their required physiological range.  The article concluded with a recommendation for further work at Shellrock to learn more about talus slope heat dynamics.

Because of ongoing highway work on I-84, plus safety concerns caused by last summer’s forest fire, all northern access to Shellrock Mountain has been closed by the Oregon Department of Transportation until 2019-20.  The closure, therefore, eliminated any hope of installing arrays of continuous temperature loggers for the study of slope temperatures and quantifying pika thermal habitat.   The situation forced an attempt to use remote temperature sensing, using LWIR (long wave infrared) images from the Washington shore for further investigation.   In retrospect, the set-back resulted in a positive new direction for this project, since early LWIR results are promising.

The remainder of this article is a randomly organized photo-journal consisting of a series of LWIR images, preliminary interpretations, and discussions of future application in the study of talus slope processes and related plant and animal habitat. All of the images used in the article came directly from the thermal camera, with no post-processing of image quality.

Overview jpg

Figure 1.  Summer 2018 Shellrock Mountain LWIR mosaic overview.

Above is a mosaic of 10 individual LWIR images of the north slope of Shellrock, collected on a hot evening in early August 2018.  The image covers a 0.56 mile reach of Oregon shoreline, and represents a good backdrop for the remainder of this article.  This and following smaller-scale images were collected after dark during evenings of hot (90-100 degF) days, for maximizing summer hot/cold slope temperature gradients.

Note the high diversity of slope ground temperatures, and typical distributions (i.e., summer cold air venting zones being typically at the base of talus slopes, but not always).  While temperature scales are shown on this and other images, use is only recommended for understanding relative temperature ranges.  This is because target temperatures are attenuated by the atmosphere and atmospheric variables over distance.  Understanding absolute temperatures or ranges might require “calibration” using in-situ slope temperature loggers and/or spot measurements.   Depending on study goals, however, simple understanding of relative temperatures within scenes may be adequate.  Other challenges in image analysis may arise from differences in target material emissivity, incidence angles, and reflection of heat coming from the sun and heated landscape.  To minimize the reflection and maybe incidence angle challenges, all images were collected at night to eliminate heat interference from the sun, which is probably the biggest cause of reflected LWIR from dry vegetation and other reflective surfaces.

Big Cold Vent

The “Big Cold Vent” is the curious cold ground feature I located on the mountain’s northwest flank in June 2017.  As hypothesized in the first article, this could be the location of a periglacial ice lens that formed within the base of the talus slope, as a result of chimney effect and Balch effect cooling.  That conclusion is based on the fact that shallow ground temperatures did not rise above freezing until early August 2017.  At the very least, it is the location of significant chimney effect cooling of the lower slope during summer.

The vent stands out like a beacon at the far right of Figure 2 below, and at the bottom of Figure 3.  Interestingly, the coldest air seems to be venting out of the east side of the humped feature, where the slope was bared by an old landslide.  The slide may date back to original Columbia River Highway or Interstate 84 construction.  This could be where the ice core was intercepted and exposed by the slide, and/or where the coldest air continues to vent from the mountain’s talus veneer. Note too that warm slope conditions are visible to the left of the cold vent, resulting in a discontinuity in the mountain’s cold basal band.  This discontinuity probably resulted from the same landslide, and subsequent removal of the material during clean-up of the slide.  The now exposed post-slide hillside may lack the talus depth and mantle porosity required for chimney effect air circulation.  This likely finding has an important real-world “management” implication, which is any dislocation of material from the base of talus slopes via talus rock mining, road maintenance, and road / edifice construction, can cause mass movements that modify or eliminate talus mantles, air and heat transfers, and dependent talus habitats.  Another example is discussed in a later section of this article.

big cold vent insert

Figure 2.  View of Shellrock Mountain and Big Cold Vent (right).

Figure 3 below shows a dominant aspect of Shellrock Mountain’s geomorphology (i.e., landscape form) that may help explain the strong cold talus effect and likely periglacial activity at the Big Cold Vent (see first article in this series).  The mountain’s west talus slope has been over-ridden by successive landslides and other slope movements during the past thousands of years.  As this deposition of mixed slope debris has occurred, the slow accumulation of well-sorted talus from the mountain’s west headwalls has continued.  Depending on what process has been most dominant, talus might overlay the mixed slope debris, or mixed slope debris might overlay talus.  Given the rate of landslide activity in the Gorge, however, it is likely that mixed slope debris deposition from the west has outpaced the slow and even generation of talus from Shellrock’s headwalls. Regardless, the photo shows that the two deposition processes have resulted in a descending truncation of the mountain cone’s talus slopes, trending from the south.  The truncation likely assumes the form of a porous, subsurface trough of talus (likely overlain by slope debris) that collects, reservoirs, and transports the dense cold winter air across and down the mountain’s west skirt in summer.  This might result in a “compound, 3-dimensional chimney effect”, where all the cold air concentrated in talus along the west side of the mountain is collected in the trough, and is ultimately transported down to the Big Cold Vent outlet just above the Columbia River.  Such compounding would not occur if Shellrock Mountain rested on a flat plane, since there would be a multitude of cold air outlets instead of only one.

The effects of this hypothesized flow of cold surface and subsurface air are visible along the right side of Photo 3, although much of cold trough is invisible due to blockage by tall trees growing on the landslide slope.  Confirmation of the compounding effect might be achieved in the future via the installation and monitoring of directional subsurface airflow meters and temperature loggers in the west slope talus and trough.

It is unknown whether pikas directly use the Big Cold Vent as habitat, as I have never observed them at the site.  It is possible that direct occupation of this and similar vents would represent too cold and unvarying temperatures, even in summer.  It is also likely that the north side of Shellrock Mountain lacks other important habitat features, such as big enough forefields for foraging and hay collection.  These features are now greatly diminished due to ever growing human development activities (i.e., highway, railroad and recreational trail developments, and subsequent maintenance, recreational trail use, train and vehicle traffic, etc.).

cold trough

Figure 3.  View of Shellrock Mountain and hypothesized cold air “trough” descending to Big Cold Vent.

Slope Temperature Profiles

The following two images illustrate use of standard IR image analysis software (i3system, Inc.) for depicting custom point, line and area temperature contrasts within scenes.  Some of the software’s basic functions, using the long-distance Washington-side images, were tried with positive results.

Figure 4 illustrates surface temperatures along the fall line, above and below the Big Cold Vent. Below the image is a graph showing pixel temperatures along the transect.  Obvious is the cold vent temperature anomaly, and elevated temperatures of the interstate highway, railroad ballast, and shoreline.   The limits of the cold vent anomaly are relatively confined from bottom to top, spanning maybe 150 feet along the fall line.  Relative temperatures along the line where it transects the upper talus slope, and even Columbia River, seems consistent.  This is despite the distance, high angles of incidence, and maybe surface reflection inconsistencies in both cases.  The shape of the curve seems to be what would be expected for a thermally active talus slope undergoing summer chimney effect heat transfer.  This remote and graphical means of charting slope temperatures may be a very suitable replacement for arrays of in-situ temperature loggers.

Collins view temp profile

Figure 4.  Fall line temperature transect.

Figure 5 shows a horizontal on-contour temperature profile of the same slope between “Twin Vents” (left) and “Big Cold Vent” (right), probably 40 vertical feet above highway level.  The main reason for including this image is due to the camera and software’s ability to detect a small diameter temperature anomaly (13.4 degC) at the cold vent (the exact position is covered by the temperature scale).  The cold anomaly is about 4 pixels wide, which at this distance would make it about 8 feet.

Collins view temp profile2

Figure 5.  On-contour temperature transect.

The opportunities for using the technology demonstrated by figures 4 and 5 for both ecologic and geologic applications are many.  First, LWIR imagery seems suitable for locating and roughly understanding thermally active slopes. In study designs, this might enable optimal placement of temperature loggers, siting of pika and other biological survey transects, etc.  To enable this, it would probably be necessary to simultaneously incorporate both summer and winter images to map the location of both summer cold and winter warm vents.  Second, IR might be suitable for use as the primary study method in geologic and ecologic studies, if imagery results were ground-truth calibrated using in-situ measurements.

Landslides and Other Talus Slope Features

Some of the big challenges in interpreting LWIR images involve segregating image effects caused by distance, target emissivity, angle of incidence, and target reflectance.  When first beginning to analyze LWIR images of Shellrock, some of the data led me to suspect that mossy slopes might correlate with areas displaying cold talus conditions.  It seemed probable that mosses would favor areas with cool, humid, uprising air currents during the heat of summer.  While probably true, images such as Figure 6 cloud that conclusion.  Here, it appears that many moss patches above the Big Cold Vent inhabit warm zones.  There are at least two possible explanations for the discrepancy.  First, mosses might be actively growing on both warm and cold slopes surfaces year-round.  Second, it is possible that while mosses inhabit both areas, the patches seen on the upper warm slopes are dormant in summer, and only lower patches are actively growing then.  Full understanding of surface temperatures will take more work to understand emissivity and reflectance occurring from active (growing), vs. dry (dormant) mossy surfaces.

It’s nevertheless clear that the images do a pretty good job of describing relative variations in landscape temperature.  The infrared image in Figure 6 clearly shows very warm near-ground temperatures under the landslide slope (right) tree canopy in the early evening.

Big Cold Vent

Figure 6.  Heat blanketed below landslide slope tree canopy (right), and “hot moss” slope above Big Cold Vent.

Figure 7 below shows additional hillside processes that can likely be analyzed using LWIR.  As noted earlier, a good percentage of the summer evening scene is dominated by warm tree canopies.  Dry mosses may also be reflecting heat from the surrounding landscape, and like tree canopies, could be masking the temperature of talus surfaces.

Most interesting is the thermal character of the fall 2017 talus landslide.  The bottom of the landslide shows as a granular and hot surface, likely due to the existence of large hot rocks with wide voids of separation.  I believe that this type of rock sorting (largest clasts settling at the bottom of slopes, with smaller clasts settling upslope) is characteristic of landslides, and is the same as occurs during the artificial end–dumping of rock during construction of fill slopes.  Assuming the effect seen in Figure 7 is typical, it would appear that neither landslides nor end-dumping are conducive to chimney effect ventilation in slopes, this being due to resulting top-to-bottom rock size gradation and overall poor rock sorting.  Furthermore, landslides in particular might preclude chimney effect action on upper slopes if the entire layer of talus slides, and only poorly sorted, fines dominated, and ultimately non-porous hillside surfaces remain.

The above observations indicate that the formation of ventilated and functional talus habitats is probably the product of the gradual accumulation and slow movement of rock material originating from headwalls.  If correct, this lends more support to the caution voiced earlier in this article concerning the need to protect the integrity of talus slopes during land management activities.  The finding could also be important with respect to the creation of artificial talus slope habitats for pika and other organisms, if creation of artificial talus slope environments is contemplated via simple, end-dumping of rock.

Landslide 1

Figure 7.  Landslide and other talus features viewed using LWIR.

The final image in Figure 8 is included because it broadcasts the complexity of Shellrock Mountain’s thermal patterns, and potential usefulness in understanding how pikas and other animals and plants use such habitat features.  But on a more basic and simple note, the image is simply a rare glimpse of the unexpected and unseen natural beauty of the Columbia River Gorge.  Note the combination of likely chimney effect cooling evidenced by cold surfaces at the slope’s base, and possibly Balch effect pooling of cold air behind the I-84 retaining wall.  The retaining wall is seen at the right, and just left of the large truck on I-84 with visibly hot wheels.

Though some of the slope surface is blocked by relatively warm tree canopies, it is obvious that summer thermal patterns in the talus landscape are varied and complex.  Not all summer cool air venting occurs at the very bottom of such slopes, and warmer areas are intermingled with cooler zones.  It is a mystery why some of the “cold air springs” visible on the image occur slightly upslope and above the usual band of cool air venting from the mountain’s base.  Could there be areas of remnant ice just under the surface, confined “artesian” air conduits leading up from the cold talus cores, or simply layers of confining material directing the cold air outward prior to it reaching the  bottom of the slope?

final image

Figure 8.  Complex summer cool venting (“cold air springs”), and Balch effect pooling on north side of Shellrock Mountain.

Going Forward

The ultimate goal of correlating pika seasonal activity at Shellrock Mountain with the mountain’s varied thermal features will be a challenge.  It seems achievable, however, if a person could overlay pika census data atop geo-referenced LWIR imagery, and then search for trends.  Such a task might be the perfect application for GIS analysis, and its ability to correlate population data to mapped features.

To get there, a method of tracking a population’s seasonal movement and activity would first be required.  Second, accurate LWIR mapping and geo-referencing of summer cool zone and winter warm zone thermal features would allow the mapping of year-round subsurface habitat temperatures.  Equating LWIR-derived surface temperatures with subsurface temperatures would be possible, given the fact that summer cold zone subsurface temperatures should be very close to LWIR-measured surface temperatures.  Likewise, winter hot zone subsurface temperatures should be very close to LWIR-measured surfaces.  This is because lower slope cold zone air venting (downward direction) is very rapid on the hottest days of summer, as is upper slope warm air venting (upward direction) during the coldest days of winter.  Venting air speeds may be as high as 300 feet per day, according to modelling reported by Jonas Wicky and Christian Hauck in their 2017 “The Cryosphere” journal article.

Finally, the overlay of population tracking information on composite summer/winter thermal maps might allow understanding of how the animals are making use of favorable thermal habitats, in conjunction with mapped foraging areas, hay storage locations, breeding dens, etc.   Final analysis may show, for example, that pika occupation and activities trend toward cold talus zones in summer, and warm talus zones in winter, as USFS researcher Connie Millar and I have both suggested possible. Millar has found that the “forefields” pikas use during foraging and hay collection are typically found at the base of cool talus slopes.  Perhaps GIS analysis would also show that hay pile storage areas (used by pikas for supplemental winter food) are located upslope or adjacent to warm vent locations, and  near areas the animals spend their winter months.  Such areas are also often snow-free in active chimney effect environments, so would facilitate more surface feeding activity in winter.

Given the fact that such variable thermal diversity exist within such a limited geographic range, it would be very surprising if pikas (an animal with seemingly limited temperature and migration ranges) did not make extensive use of the compact thermal diversities offered in talus slopes.

Acknowledgements:

I would like to sincerely thank Dr. Connie Millar of the USFS Pacific Southwest Research Station in Albany, CA for her interest, review, and comments on the draft article.  Technical comments are likewise welcomed from anyone else on this version. 

Mouseland

Cover of 1901 book by Edward Earle Childs

 

When U.S. Captain George B. McClellan traversed Washington’s Cascade Mountain Range in 1853 (nine years before he would briefly serve as general-in-chief in Lincoln’s Union Army), his wagon train was well equipped with a trained naturalist, other scientists, artists, interpreters, and native guides.  The main purpose of his “Northern Survey” was to locate a possible transcontinental railroad route, but a secondary reason was simple scientific and ethnographic exploration of the American west.

The McClellan Survey began at Ft. Vancouver, Washington on June 15, 1853, and worked its way up the Columbia River until veering north into the Cascade Range west of Trout Lake, Washington.  In mid-August, the expedition encountered a curious landscape dominated by a long series of lava caves, natural bridges and rough-bottom trenches, stretching along a 12 mile line from the Big Lava Bed eruption cone down to the present site of Trout Lake, Washington.   Modern day travelers retrace the route via driving State Highway 141 west of Trout Lake, merging onto USFS Road 24 along Dry Creek to Peterson Prairie, then continuing along roads 60 and 66 to the South Prairie vicinity.  Along the path are found the current day “Trout Lake Ice Cave” and “Natural Bridges” waysides.

During the Holocene epoch (6,200-8,200 years ago) lava eruptions from the Big Lava Bed cone flowed east-northeast toward Trout Lake.  During one such flow, the surface cooled and crusted over (much as a cold mountain stream might freeze-over from the top), thus creating a sub-surface conduit carrying the stream of molten rock.  Once the eruption stopped, the underground conduit drained of lava, thereby creating a long vaulted underground passage.  In the centuries that followed, some long sections of the passage collapsed forming open trenches with boulder-strewn floors.  Other short sections remained standing as “lava bridges”, while other longer sections of standing conduit resulted in what we now term “lava caves”.

When arriving in the region, the 1853 expedition’s first source of knowledge would have undoubtedly come from their native guides, plus contacts they had with the native people who inhabited the high country around Mt. Adams in summer.  As a result, the expedition was able to describe the area traversed, and record local American Indian mythologies that told of the origins of the terrain.  The following transcription is one such origin myth, copied directly from the 1854 Annual Report of the Commissioner of Indian Affairs to the US Congress:

“In descending the valley from Chequoss (note, historians conclude this is likely Indian Heaven), there occurs beneath a field of lava a vaulted passage, some miles in length, through which a stream flows in the rainy season, and the roof of which has fallen in here and there. Concerning this, they relate that, a very long time ago, before there were any Indians, there lived in this country a man and wife of gigantic stature. The man became tired of his partner, and took to himself a mouse, which thereupon became a woman. When the first wife knew of this, she was, very naturally, enraged, and threatened to kill him. This coming to the man’s knowledge, he hid himself and his mouse-wife in a place higher up the mountain, where there is a small lake having no visible outlet. The first woman, finding that they had escaped her, and suspecting that they were hidden under ground, commenced digging, and tore up this passage. At last she came beneath where they stood, and, looking up through a hole, saw them laughing at her. With great difficulty, and after sliding back two or three times, she succeeded in reaching them, when the man, now much alarmed, begged her not to kill him, but to allow him to return to their home, and live with her as of old. She finally consented to kill only the mouse-wife, which she did, and it is her blood which has colored the stones at the lake. After a time, the man asked her why she had wished to kill the other woman. She answered, because they had brought her to shame, and that she had a mind to kill him, too; which she finally did, and since when she had lived alone in the mountain.

Another story about the same place is to the effect that it was made by a former people called the Seaim, a name corresponding with the jargon word for grizzly bear. The mouse story seems to be interwoven with the Klikatat mythology; for, besides the name of this place, Hool-hool-ilse, (from hool-hool, a mouse,) one of the names of their country, is Hoolhoolpam, or the mouse-land. This is given to it by the Yakamas…”.

Consideration of this historical source leads to the remarkable conclusion that the Yakama people of the mid-1800s most associated their allied Klickitats with a land dominated by the presence of some small animal, whose common name was translated by expedition members to mean “mouse”.  But was the land’s ubiquitous namesake truly a mouse, or even a member of the rodent family?  Or, given all the verbal and written translations and transcriptions involved in capturing the archetypal myth, did the expedition err in nomenclature?

It is certainly true that many rodents live in association with blocky rock environments like collapsed lava tubes, lava bridges, lava caves, lava plains, mountain sides, and talus slopes in the Pacific Northwest.  Rodents found in such areas include marmots, pack rats, chipmunks, ground squirrels, deer mice and others.  But to anyone who has spent time along this section of the McClellan Trail, it is obvious that Mouseland (hoolhoolpam) must instead be reference to the American pika.  Evidence of this is expressed by the currently high concentration of these members of the rabbit order (Lagomorpha) that inhabit the area, plus the fact that many Mouseland cave names reference this very visible and audible animal.  Current day place names include “Pika Here Cave”, “Pika Ice Cave”, “Squeaking Pika Cave”, and even “Chubby Bunny Cave”.

Along one lower reach of lava trench separated by bridges and caves, I have noted pikas in nearly every trench section, often in close proximity.  Pikas are territorial and usually widely dispersed on open talus, but perhaps the many deep trenches separated by basalt walls and rubble results in sufficient isolation without the usual distance seemingly required on open talus slopes.  As is often the case, perhaps “good walls” make “good neighbors” in the pika community.  Overall, my informal surveys have recorded the animals along at least half of the Mouseland reach, from 2400 to 3000 foot elevation.

Pikas, like all organisms, are subject to strict habitat criteria, including specific temperature ranges.  Their temperature tolerances are likely narrower than many other mammals, simply due to the fact that early members of their family (Ochotonidae) evolved in association with highly buffered temperature environments, typified by natural cooling and heating mechanisms (e.g. Chimney and Balch effects), constancy of the earth’s heat, plus the insulation afforded by winter snow cover and blocky rock deposits.  There is a huge metabolic efficiency advantage bestowed upon animals that can evolve in association with such environments, given the fact that the calories normally required for keeping warm and cool can be devoted to other important life activities such as acquiring food, reproduction, resting, reflection, and even play.

The drawback of genetic adaption to a narrow physical environment (i.e., habitat) is that it means such organisms are unable to venture far from that physical range.  Thereby, a state of what’s called “endemism” comes to exists.  Endemism is defined as a species’ ecological and genetic state being unique to a limited geographic location, or habitat condition.  Such species display relatively small geographic ranges consequent to their highly specific habitat requirements, and inability to migrate far from their “islands”.  Some highly endemic species such as ice crawlers (or grylloblattids) have very small species distributions, many being less than 100 square miles.

All of this leads to the difficult question of whether seemingly protected but narrow temperature range (stenothermal) organisms like pikas are at greater risk of extinction due to global warming than wider temperature range (eurythermal) organisms, such as tree squirrels.  On one hand, the cave and rock dwellers exist in a very stable temperature controlled habitat that is highly “decoupled” from ambient conditions at the earth’s surface.  It’s logical to assume that these sheltered but temperature-limited organisms can survive regular, short-term climatic cycles in place, perhaps better than more eurythermal forms.  On the other hand, if these short-term cycles of variability end-up trending toward consistently higher ambient temperature norms, this could result in a small but significant change in the subsurface environment, and be enough to put highly sensitive endemic and stenothermal species like pikas and grylloblattids at an even higher risk of extinction, especially since migration to new “islands” of suitable habitat is nearly impossible.

Thermal Imagery for Investigating Talus Processes and Locating Pika Habitat?

 

Last summer’s Eagle Creek fire, plus a huge construction project along Interstate 84, greatly hampered on-site investigation of Shellrock Mountain’s thermal features and pikas.  Without access for installing sub-surface and surface temperature loggers, I had to look for a more remote means of investigating the behavior of Shellrock’s unique (possible ice-cored) talus mantles. This was probably fortunate, since it eventually led to consideration of the use of long wavelength infrared (LWIR) imaging for documenting variations in slope temperature, chimney effect thermal processes, and ultimately the identification of potential American pika habitat at Shellrock and other places in the Columbia River Gorge.

Having never used infrared imagery, I initially wondered whether anyone had attempted similar use.  Geological applications are certainly not billed front-and-center by any of the major manufacturers.  Nor did it appear that talus slope investigators had used it for analyzing the chimney effect, periglacial features, or other thermal slope processes.  (I learned, however, that at least one investigator (Aaron Johnston of the USGS) is beginning to use a drone-mounted infrared camera for understanding slope-specific habitat processes related to pikas).  The only other real geologic and ecologic applications I came across were for the study of glacier behavior, soil temperature, evapotranspiration, location of wildlife, crop and plant community health, and maybe a few others.

In July 2018, I purchased a non-cooled, 640×480 pixel resolution LWIR camera from the South Korean company, i3system, Inc.  Like most makers, the bulk of this company’s research and production is geared toward military and police products for surveillance, industrial product inspection, medical health diagnosis, building inspection, and various night vision purposes.  And as with many high technology gadgets, infrared equipment specifications are getting progressively better, even as costs decline.  Today’s 640×480 resolution (0.3 megapixel) thermal cameras might cost several thousand dollars, whereas only 2-3 years ago the price was tens of thousands.

Why the high cost of thermography cameras?  First, there isn’t a broad demand, so companies can’t sell enough units to justify the high initial research and production costs.  This is exacerbated by differences in the silicon chip-mounted (light vs heat) sensors. Standard photography camera sensors are based on a matrix of photo-detectors that transduce visible light intensities and wavelengths into electric signals.  Thermography camera sensors, on the other hand, use a different technology based on a matrix of chip-mounted thermometers that actually measure the temperature of each pixel that passes through the lens (an amazing 307,200 such thermometers in the case of a 640×480 resolution chip).   This data is then processed and interpreted as the surface temperatures of the objects being charted.  A final cost factor relates to the use of the rare and costly element known as germanium (instead of silicon) for the camera’s primary optics.  Interestingly, while visible light is freely transmitted through silicon dioxide glass, it largely blocks the transmission of heat radiation.  Instead, elemental germanium or Ge02 (germanium based glass) are used in the manufacture of LWIR camera optics, materials that are incidentally opaque to visible light and oddly have the appearance of polished metal.

Soon after beginning to research the use of thermal imaging for assessing Gorge talus slopes, I learned there were many limitations that could result in failure.  Foremost were the relatively great distances I would be forced to photograph the slopes from.  Oregon-side targets would need to be photographed from the Washington shoreline, and depending on river width and talus slope location, the distances would generally range between ½ to 1 ½ miles.  Such distances could be concerning, given the relatively low pixel resolution of affordable thermal cameras, and likely inability to detect even relatively large targets at such distances.  Adding to this was the fact that heat radiation from distant objects is attenuated by the atmosphere and certain atmospheric conditions.  Many times, however, the specific project goals have less to do with measuring the actual temperature of distant target, and more to do with detecting apparent temperature differences between objects in the scene.

Given these limitations, I decided that the moderately high resolution (640×480) i3System Inc. camera mounted with a relatively narrow angle 35 mm lens, would most likely provide decent resolution of small targets at distance.  Plus, given the fact that I was mainly interested in detecting relative temperature differences related to chimney effect venting on talus slopes, the possibility of inaccurate spot temperatures was of little concern.

After about one month of experimenting with the new camera, it is obvious that the technology can be very valuable in the study of how mountain slopes interact with (and influence) their physical and biological surroundings.  The header image is a fun example of the technology, showing a Union Pacific train on the Oregon side as it passes in front of a patch of cold ground at the base of Shellrock Mountain.  The photo was taken at 10:00pm, August 8, 2018, at a distance of 0.55 miles, or 2900 feet.  What does the image show in regard to eventual project capability?  First, the camera’s resolution allows interpretation of objects as small as the 40” diameter railroad car wheels from 0.55 miles. Good detection, in this case, is due to resolution plus the significant temperature difference between the train’s hot wheels and cool slope background.  Zooming-in on the image even shows some details of the new rock-fall fence along I-84.  Second, the image allows fairly easy interpretation of trees growing on the slope, and other background features.  Finally, and most important, the image allows easy understanding of relative slope temperature differences.  What looks like a white plume being emitted from the train’s locomotive is in reality cold ground in the slope behind the train.

A soon coming article will highlight the emerging results of using thermography for the study of talus features pertaining to pika habitat.

 

 

 

 

 

 

 

 

 

Low-Elevation Pikas on Wind Mountain

The twin quartz diorite domes of Shellrock Mountain on the Oregon side, and Wind Mountain on the Washington side of the Columbia River (river mile 157), have much in common.  Last summer, I noted a couple of large talus slopes on Wind’s south slope that discharged cool air from their bases.  As described in the previous article, this flow of cold air during the heat of summer is indicative of an interesting thermodynamic mechanism known as the “chimney effect”, witnessed in many talus slopes around the world.  Also proposed in the earlier article, the mechanism could be the key reason American pikas (a typically high elevation species at this latitude in the American west) occur at near sea-level in a twenty-mile segment of the western Columbia River Gorge.

Upon subsequent surveys of Wind Mountain’s south facing slope, however, no pikas were audibly detected.  This finding seemed to fit the observations of others, who recognize that low-elevation pikas exist mainly on the Oregon side of the Columbia. (That said, they have also been recorded at Cape Horn, some 20 miles WSW of Wind Mountain, and perhaps elsewhere on the Washington side).

With more thought, it occurred to me that if low elevation pikas were to exist at Wind Mountain, they would likely be found on its north or northwest flanks…  on slope aspects and angles analogous to where they appear on the Oregon-side Shellrock Mountain.  Sure enough, in early June 2018, I noted two pika calls from an individual(s) living at about 650 foot elevation on the northwest skirts of Wind Mountain, and near the base of a prominent and steep talus slope.

This observation supports the following conclusion:  the relatively high concentration of low-elevation pikas living on the Oregon side of the Columbia River Gorge is solely due to Oregon’s higher incidence of steep, north-facing, low-elevation talus slopes than occur on the Washington side.  While likely unproven at this point, it seems probable that this explanation is a given.

Why slope aspect (and probably angle) is such an important habitat consideration could be a difficult thing to quantify and understand. Certainly, north facing slopes in the northern hemisphere are simply more shaded and cooler at the surface than south facing aspects.  As referenced in the prior article, however, perhaps aspect/angle dictates the intensity of chimney effect cold air talus recharge in winter, and consequent sub-surface cool air circulation in summer (and maybe equally important, warm air circulation in winter).  Perhaps too, northern exposures are critical to the existence of suitable moss covers, which can both insulate slope surfaces from summer heat gain and maintain confined conduits for seasonal air recharge inside talus slopes.  And finally, it is certain that aspect/angle influences plant communities and their ecologies, and specifically the offering of suitable year-round forage for pikas.  All are likely factors, but there are probably others that fit into the equations that define suitable pika conditions.

If any readers of this article have noted “low elevation” pikas on the Washington side of the Gorge’s pika belt, providing this information via comments below, or email, would be appreciated.

 

Ice Mountain —  A Theory of Why Pikas Exist in the Columbia River Gorge 

Ice Mountain:  “Little Blow Holes”  —  Chapter 1

Everything below belt-line felt cold as I climbed up the lower flank of the Gorge’s Shellrock Mountain on the morning of May 28, 2017, on a day that would eventually become hot and still.  I was completing the second day of a survey for American pikas, the rabbit-related, talus-dwelling mammals so characteristic of high-elevation and cool-temperature zones of the American west.  Oddly, the species exists in the Columbia River Gorge at lower elevations (almost sea level) than anywhere else in the US.  Why has remained a mystery.

As I continued scanning the talus slope and forest margins, I saw that all the leaves within three feet of the ground were being agitated by the steady flow of cold air flowing downhill, like a sheet-flow of water over the land surface.  The air above that three foot level was contrastingly motionless and relatively warm.  Upon bending down into the cold layer and examining the talus surface, I felt the cold air emerging from the talus itself, springing like invisible water from the countless openings.

What was causing the generation and emission of this near freezing air, and could it somehow be related to the seeming out-of-place existence of cool-loving pikas at near sea level in the Gorge?  My interest grew as I walked back down the old road from the survey site.

The Cool-Loving Pika

Most everyone who has hiked, climbed or driven through the high mountainous regions of the western US has treaded upon American pika territory.  In the northern coastal regions of British Columbia, the populations range from near sea level to over 13,000 feet in those high and cold latitudes.  Farther south, in the lower latitudes of Nevada and California, the lower limit of their range begins at about 6,000 feet.  In our portion of the central Cascade Mountains of Washington and Oregon, pikas commonly occur at elevations of 4,000 feet to above timberline.  Here in the Gorge, however, many people have been surprised to hear their familiar call along the Columbia River near sea level, at places like Shellrock Mountain, Herman Creek, and even the heavily used trails around Multnomah Falls.

There are many fascinating aspects of pika biology, but the chief consideration of this article is their narrow range of temperature tolerance.  Pikas, like other members of the rabbit family (i.e., lagomorphs), are limited in their ability to regulate body heat.  Most important, they are unable to cool their body temperature by panting or sweating.  If unable to find thermal shelter and shade on a day humans might find comfortable (i.e., 78 degrees F), they can become stressed (hyperthermic) and die in as few as six hours.  Nor do they tolerate extreme cold, and researchers have concluded that they are dependent on long-lasting winter snow packs above their winter dens to provide igloo-like insulation from cold air and the rigors of rain and freezing rain.  This has led researchers to conclude that extreme temperature (both high and low) is likely the most important ‘limiting factor’ determining what elevations and latitudes pikas can survive. At first glance, it would seem doubtful that pikas could survive in the lower elevations of the Gorge, because summer air temperatures can be very warm, and winters have periods of extreme cold, no snowpack, heavy rain and periods of freezing rain.

Pika in Columbia River Gorge near Shellrock Mountain

Photo credit:  Will Thompson/ USGS

Pikas do not hibernate.  Instead, they keep their heat-generating metabolism going throughout the winter by staying active and subsisting on a wide variety of plants foraged and stored in “hay piles” during the previous summer.  In accord with their unique physiology, they have evolved a partially underground lifestyle, similar to cave dwellers.  And in actuality, the talus rock pockets they inhabit are like caves with respect to having relatively constant and moderate year-round temperatures.  Talus is essentially blocky rock debris that has been shed from steep mountain walls, which gradually accumulates in pediments along the lower mountain slopes.  Because the rocks are relatively uniform in size, there is considerable open space between the blocks that insulates the interior pockets from sun exposure, wind, moisture, and other outside conditions.   While pikas spend a great deal of time outdoors collecting and eating plant forage, they are highly dependent on their buffered, underground pocket environment for year-round protection from predators, rearing their young, keeping dry, and especially escaping the extremes of summer heat and winter cold.

But if explaining pika presence in the lower elevations of the Gorge was solely based on their biological adaption to use of talus shelter, why is the population mostly restricted to the 20 mile-long, Oregon-side segment between Multnomah Falls and Shellrock Mountain?  In fact, seemingly suitable talus geologies occur throughout the Gorge, both east and west.  The answer to the pika riddle must be approached broader, and in the context of a complex biogeography question.

Biogeography is one of the more interesting realms of biological science, as it merges the fields of ecology, climate, geology, evolutionary biology, and physical geography to explain why species occur in specific patchworks on the landscape. It is a field that originated with the early exploration of our planet, when great European expedition-based biologists like Alfred Russel Wallace began noting and trying to explain why plant and animal communities changed with latitude, elevation, aspect, and other characteristics of the geographies they traversed.

The more I thought about what I had seen at Shellrock Mountain on that soon to be hot Gorge day, the more I suspected that the mountain’s breath of cold air might hold the answer to solving the pika riddle.  Before long, I was driving back east along the 10 mile stretch of interstate I-84 leading to Hood River and White Salmon, with questions for Google and knowledgeable scientists.   What I subsequently learned, and the theories hatched to explain the Shellrock situation, will be outlined in the following chapters dealing with heat transfer in talus slopes, permafrost, Gorge history, and Gorge meteorology.

 

Ice Mountain:  The Chimney Effect — Chapter 2

Some hillsides, like all caves, inhale and exhale air due to how differences in outside temperature and barometric pressure act upon their interiors.  Air pressure and temperature changes that occur in mountain features like talus slopes have been most actively studied by scientists in mountainous regions of the world (particularly in the Alps of Europe), where landscapes are dominated by high peaks and valleys, and the understanding of glaciers, permafrost, rock falls, talus slopes, and water supplies is critical to living in such places.

Upon noticing the unusual venting of cold air from the lower slopes of Shellrock Mountain, I returned home, and began reading the findings of the various scientists involved in the study of talus slope dynamics.  I learned that there is indeed a well-documented physical process observed in “cold talus slopes” that causes them to draw cold air into the toe of the slope in winter, and emit cold air from the toe in summer.

This reversible air circulation process, known as the “chimney effect”, was first scientifically described by Alpine explorer Horace-Bénédict de Saussure in the 16th century, after observation of out-of-place ecologies, including cold-stunted trees, dwarf forests, mosses, and typically higher elevation plant species, at the bottom of some mountain slopes.  And too, people even before Saussure’s time would have recognized and found economic uses for cold talus, including the storage of perishable foods and ice during the summer.

Swiss researchers Sébastien Morard, Reynald Delaloye, and Christophe Lambiel describe the cold talus chimney effect in their 2010 paper from Geographica Helvetica, entitled “Pluriannual thermal behaviour of low elevation cold talus slopes in western Switzerland”, a portion of which is quoted below.

Variations of both direction and velocity of the airflow in accumulations of loose sediments are primarily controlled by the thermal contrast between the outside and inside (ground) air causing a gradient of driving pressure.  The airflow direction reverses seasonally. During winter, an ascent of relatively warm light air tends to occur in the upper part of the debris accumulation. This leads to a dynamic low (a depression) in the lower part, causing a forced aspiration of cold external air deep inside the ground even through a thick – but porous – snowpack.  A gravity discharge of relatively cold dense air occurs during summer in the lowermost part of the debris accumulation, preventing the ground surface temperature from rising significantly above 0°C in this section of the loose sediment accumulation.  As a consequence, a diffuse aspiration of external warm air occurs in the upper part of the slope”.

A diagram from their paper that illustrates the process follows.  The abbreviation Tao indicates outside air temperature and Tai indicates temperature inside the talus slope.

 

Chimney effect diagram

These and other researchers have shown that the chimney effect is a process that can be responsible for the formation of perpetually frozen ground (permafrost) and ice in the base of some cold talus slopes.  This sub-zero temperature anomaly is accompanied by a corresponding warm zone in upper sections of the same slopes.  Interestingly, the emission of the upward trending warm air from the slope’s interior can be witnessed in winter by the absence of snow surrounding the warm vents.  A well-studied example of cold talus is found at the Creux-du-Van talus slope in the Jura Mountains of Switzerland at an elevation of about 3500 feet, which is significantly below the 8000 foot level of discontinuous (i.e., sporadic) mountain permafrost for this latitude in the Alps (about the same latitude as Mt. Rainier).

On first impression, the formation of ground permafrost and ice seems impossible in places like Creux-du-Van, where mean annual air temperatures are 42 degrees F, and regional mean annual ground temperatures are also well above freezing.  Year-round ice seems further unlikely in ground where cooling must first overcome the earth’s natural heat.  The recognized explanation for this mysterious cooling is that the chimney effect can cause drastic over-cooling at the base of the slope in winter, enough to surpass summer heating.  The effect is enhanced when fall and early winter snow packs are lacking while temperatures are below freezing.  This allows cold air to freely enter at the beginning of winter, and become later trapped by the snow cover.  The colder the ambient winter air, the bigger the thermal gradient between the inside and outside of the slope, and the faster cold air is drawn up into the slope’s base.   Likewise, the warmer the summer, the faster the upper portions of the talus slope are warmed in response to cold air draining from the base.  Researchers also comment on the existence of a moss layer covering the bottom of cold Alpine talus slopes, similar to what we witness in the Columbia River Gorge.  The observation is of interest, since not only is the moss dependent on the slope’s output of cool air, but it may also be responsible for the cold talus effect since it insulates and seals the surface of the porous talus so that it can act as a defined conduit for air exchange.

About one month after my first notice of apparent cold talus at Shellrock, I again travelled to the site on the hot afternoon of July 5, 2017, armed with a long-probe electronic thermometer, to try to measure the temperature of the cold air draining from the talus veneers on the mountain’s north side.  Cold air was found to be venting from many of the mountain’s talus slopes, most in the range of 40 degrees F.  As the day was ending, I decided to try to sink the temperature probe into the base of one last slope.  Soon, and to great surprise, the thermometer’s screen displayed a snowflake symbol, indicating that the probe had encountered a truly frozen zone only one foot below the rocky surface. This same monitoring site continued to show sub-freezing conditions until the first week of August, at which time the foot-deep temperature began to rise slowly above 32 degrees F.

Here, with discovery of an apparently active chimney effect, it was starting to appear that cold talus was indeed present at Shellrock Mountain, and quite possibly deep permafrost.  With this, the riddle posed in the first chapter (i.e., how is it possible that American pika can survive in the low and warm elevations of the Columbia River Gorge?) seemed to be gaining a possible explanation.  But with this discovery, a much larger ultimate question arose:   how was it possible, in the first place, that strongly cold talus and likely permafrost could be present at this incredibly low altitude (120 feet above sea level) and at this middle latitude?  This question will be explored in the fifth chapter, which deals with the theory that our unique Gorge climate and topography may be responsible.  Before that, however, the next chapter will explore the possibility that the landform I had come across was a periglacial rock/ice feature.  The fourth chapter will explore whether any historical records may support the existence of ice and periglacial activity at Shellrock Mountain.

 

Ice Mountain:  Periglacial Ice on Shellrock Mountain? — Chapter 3

One western scientist’s findings have special relevance to understanding pika presence in the Gorge.  Connie Millar of the US Forest Service’s Pacific Southwest Research Station in Albany, California has researched the ecology of American pika in the talus landscapes of the Sierra Nevada and western Great Basin for the past 15 years.  Her work has centered on development of rapid assessment protocols for identifying potential pika habitat via on-site analysis of climate, ground temperatures, landscape type and geology.  With such understanding, the USFS hopes to improve its ability to decide whether certain land management strategies will have impacts on pikas, possibly under a changing climate.

During examination of hundreds of rocky pika occupations in the Sierra Nevada and Great Basin (at altitudes ranging from 5,593 to 12,752 feet), Millar concluded that most (82%) are in close proximity to rock glaciers or similar rock/ice (i.e., periglacial) features.  Also observed was the fact that pikas are typically found near the base of ice-cored talus slopes and rock glaciers, given the presence of both suitable thermal habitat and proximity to the forefields they use to collect forage. Based on this, Millar has confirmed that such rock/ice periglacial habitats are optimal for American pika

I first began suspecting that the cold talus feature found at Shellrock might be ice-cored talus after reading descriptions of these geologic features, and revisiting the site for closer examination.  Although much debated, most geologists agree that year-round ice can form in mountainous or arctic terrains as a result of two distinct processes.  The first is termed “glacial”, which is the familiar process that starts with snowfall, snow accumulation, and gradual transformation to solid ice as snow depth increases.  The second process is known as “periglacial”, which is not dependent on snow accumulation.  Instead, periglacial ice is formed when precipitation or melt water enters and freezes within an already frozen underground rock or soil matrix.  Common types of periglacial features identified by geologists include rock glaciers, boulder streams, ramparts, patterned ground, and ice-cored talus.

The Shellrock Mountain feature seems to fit the description that geologists have assigned to periglacial ice-cored talus, or potentially a very small rock glacier.  It occurs at the base of a massive talus slope, displays a slightly over-steepened front face and sidewalls, is longer than wide, and appears to be frozen.  Finally, it shows signs of past movement, which during construction of Interstate 84 during the 1950s-1960s required construction of a steel reinforced earth wall to protect the highway.  I hypothesize that periglacial ice forms here when precipitation falls on upper portions of the slope, sinks into the relatively warm upper talus interior, flows downslope along the bedrock interface, and finally intercepts freezing temperatures in the lower core.  It is likely that most of the water infiltration and freezing occurs in winter with the on-set of cold temperatures, rain, and snow.  Remember that chimney effect cooling is highest during winter, when cold air is actively drawn into the base of the slope while warm air is discharged from the upper slope.

 

Ice Mountain:  “Shellrock Mountain Rests on Ice” — Chapter 4

Upon finding documentation of the formation of periglacial ice at the base of some low-elevation talus slopes in Europe and elsewhere, I became interested in monitoring the Shellrock slope using the methods of European researchers to prove the existence of ice and permafrost.  But before that investment of time and money (or trying to convince others to be party to it), it made sense to first determine whether these conditions had ever been reported at Shellrock Mountain or other Gorge locales, perhaps during a colder climatic past.   Had earlier pioneers noted this apparently remarkable geological feature?

One well-known Columbia River Gorge historical event immediately came to mind, that being the winter 1884-85 stranding of a passenger train between Shellrock Mountain and Starvation Creek (see 1922 photo below, courtesy of The History Museum of Hood River County).  During that unusually harsh winter, an east wind-driven storm resulted in 15-20 foot deep flows of ice pellets that froze into one solid mass of ice, eventually requiring blasting to remove.  Passengers were stranded for 3 weeks, until the good citizens of Hood River were able to come to their rescue with picks, shovels, black powder, and food.

Starvation Creek stranding near Shellrock Mountain

Photo Credit:  History Museum of Hood River County

While it does not seem likely that this specific type of weather pattern could be responsible for the buildup of periglacial ice, it is indicative of atypical meteorological patterns in the vicinity of Shellrock Mountain that still occur.  Travelers along I-84 witnessed smaller deposits of welded ice pellets in this area as recently as spring 2017, and long after evidence of ice and snow had disappeared from other Gorge locales.  ODOT maintenance crews at Cascade Locks still consider this stretch of road their worst winter maintenance challenge.

Upon continued research, it was exciting to find a much more relevant reference to potential periglacial ice contained in William H. McNeal’s 1953 book entitled “History of Wasco County”, which relates stories from construction of the early roads through the Gorge.  In one chapter, McNeal describes the almost insurmountable barrier posed by Shellrock Mountain to construction of the 1915 Columbia River Highway.  Within that passage, McNeal states “Shellrock Mountain rests on ice”.  With that exciting tidbit, I began contacting people who might have engineering records going back to construction of the first roads, including the Historical Columbia River Highway.

Of all the people contacted, the most valuable assistance came from Kristin Stallman, who until recently worked as ODOT’s Historic Columbia River Highway Trail project coordinator.  I soon found that Kristen maintained a large library of historical information related to construction of the old highway.  The first document she provided gave strong support to the statement made in McNeal’s book.  This was the transcript of a 1967 interview conducted by historians Ivan Donaldson and Wayne Gurley, with Glenn Kibbe and Marshall Newport, two men who had actually worked on construction of the highway.  Kibbe headed the construction company “Kern and Kibbe”, which had the contract to build the section of the Columbia River Highway between the Multnomah line and the City of Hood River.  His interview documented many problems encountered during construction, many revolving around the impacts of excessive water on slope stability at places like Ruckel Creek and Herman Creek.  Beyond that, Kibbe, Marshall, and the interviewers devoted a lot of discussion to ice and water-related talus instability at Shellrock’s west end.  I was especially excited to come across the portion of the interview inserted below, which seems to describe the slope that is the subject of this article:

“Gurley:   I was wondering when they were working on the highway down here they took a lot of material off that sliding slope where it had been sliding so bad and right in there. When I came over here a fellow took me back there and there were little openings in the rock and you could feel the cold air rushing out of there just as if it was off of ice.  Kinda like little blow holes.

Newport:   Ice is supposed to be in there, isn’t it Glen?

Gurley:   And that’s where they found it, according to drillings”.

Gurley’s reflections on 1915 are very telling.  First, it’s obvious that more than a century ago, he had witnessed the same strong cold talus effects that I observed on May 28, 2017.  Second, he provided evidence that engineers and/or contractors working on construction of the Columbia River Highway intercepted ice during either construction or exploratory drilling.

A further exchange from the interview gives still more historical evidence of subsurface ice at Shellrock.  This portion is of special interest, given that Kibbe ventures to say the ice was not “glacial”.  With that, he was likely saying that the ice was not laying on the surface in a pure state, as might be seen on the glaciers of Mount Adams or Mount Hood.  Instead, he seemed to be describing an ice feature that had a large percentage of rock and soil material in its composition.  Indeed, his description better fits the appearance of thawing, shallow periglacial ice, perhaps a geological process known as solifluction occurring over the slope’s frozen core.

“Kibbe:   I wonder if there’s still ice in that mountain?

Gurley:   From what most of the geologists say, I think there is.

Kibbe:   When I was here in 1917 up to 1920, while I was here, this this stuff was not like a glacier. It was like what you might call a melting ice and that’s where you got your slides. In the summer she’d get warm and melt, bring down gravel all the time. We built high walls to catch it, but I guess they all filled up and I guess they had to take them out”.

 

Ice Mountain:  A Wind Gap Between Wind Mountain and Shellrock Mountain — Chapter 5

Windsurfers, fishermen, barge pilots and even motorists have experienced the turbulent culmination of Gorge topography and weather occurring west of the narrow gap that constricts the Columbia River between Wind Mountain to the north and Shellrock Mountain to the south.  At only one-third of a mile across, this gap is the narrowest found along the Columbia River as it cuts through the Cascade Range between the cities of Cascade Locks and Hood River.  The north-south trending Cascade Range crest is such a dominant landscape feature, it actually creates separation between the Pacific Northwest’s two major climatic patterns, the wet maritime regime to the west and the dry continental regime to the east.  Very important to the context of this article, the Columbia River constitutes the only near sea level pathway through the Cascade Range, and represents a very active air conduit between these two major climatic regions.

The individuals having perhaps the most knowledge of Columbia River Gorge weather are Justin Sharp, who as a graduate student at the University of Washington, worked with Professor Clifford Mass to publish a detailed 2004 article entitled “Columbia Gorge Gap Winds: Their Climatological Influence and Synoptic Evolution”.  Not surprising, the main aspect of Gorge weather they examined was the east wind pattern of winter.  Most of the background information in the next paragraph can be attributed to their work.

Easterly “gap winds” in the western Gorge are partially driven by eastern high-pressure systems pushing dry and cold continental air to the west, and western low pressure systems pulling air into the maritime area west of the Cascades. While these large-scale “synoptic” weather patterns often initiate the westward flow, the wind can be strengthened by the unleashing of large masses of cold and dense air from the Columbia Basin, which flows hydraulically (by gravity) down the Columbia River valley from its contributing basins.  As we all know, these miserably persistent east wind patterns are often accompanied by atmospheric inversions, and weeks when the entire Columbia Basin and eastern Gorge is overcast.

An air inversion is simply a weather pattern characterized by a layer of warm (and therefore relatively buoyant) air above a layer of dense cold air at the land’s surface.  As this huge but thin layer of cold and dense air moves west, it becomes deeper as it dams-up against the Cascade Range, and surface air pressures become even greater.  Consequently, the cold air begins to rush through the narrowest parts of the Columbia Gorge and the lower passes through the Cascades.  The air movement results in high velocity gap winds in the western Gorge that commonly exceed 35 mph, but occasionally gust to over 100 mph at places like Crown Point.  As the air moves through the gap, it increases velocity while moving from high to low pressure in a very short distance.  In a recent correspondence with Sharp, he related that the pressure differentials that develop at the Wind/Shellrock gap may be as high as one millibar over a distance of three kilometers, which is higher than most meteorologists think even possible.

While the Bernoulli equation would forecast that the highest wind speeds occur in the narrowest part of the wind gap, Sharp states that the highest speed (and most turbulent air movement) is actually found west of the gap’s exit point.  Also on the leeward side of the gap, drastic vertical air movements and turbulence are caused by deflection off ridges and high points, widening of the Gorge below the gap, and formation of “mountain waves” below the gap and barriers.  As a result of the descent and rapid mixing of air at and below the inversion, any clouds present west of the crest typically dissipate as the air rushes through the gap and on toward Portland and the ocean under clear skies.

It’s therefore apparent that some very unique and drastic changes in Gorge meteorology occur adjacent to Shellrock Mountain during the coldest periods of the year, perhaps capable of driving the supercharged overcooling of talus slopes required for the formation of periglacial ice.  But how might this occur?

A simple thought experiment could present part of the mechanism.  Let’s suppose that two hot air balloonists were brave enough to make matching flights from either side of the Wind/Shellrock gap during a typical Gorge east wind event.  One launches into the overcast inversion from Cooks Landing about one mile east of the gap, as the other launches into the clear skies from Wyeth about one mile west of the gap.  The one launching from Cooks would ascent fast through the cold and dense air near the surface, until he met the warmer air above.  At this point, his ascent would slow or even stop because of the slight relative difference between the temperature inside his balloon’s envelope and the temperature of the warm air above the inversion boundary.  The balloonist launching from Wyeth would have a much different ride as his flight progresses.  His initial rate of ascent would be about the same as the balloonist at Cooks, given the ground temperatures at the two locations are equivalent and the two balloon envelopes were charged to the same temperature.  His ascent would not slow or stop, however, at the elevation of the now absent inversion boundary.  Instead, he would continue rising quickly, as long as the temperature within his balloon’s envelope was warmer than the surrounding air.

low elevation temperature inversion scenario at Wind/Shellrock gap

Diagram courtesy of www.flight.org

Just as a balloon’s flight is liberated skyward with the elimination of an air inversion, so might the upward flow of warm air within a western Gorge talus slope, since both are controlled by relative differences in temperature between the outside and inside.  During the winter (as depicted by the figure in Chapter 2), heat stored in the upper slope from the prior summer rises within the interior air to the top of the slope where it discharges.  As this occurs, a dynamic low is created at the bottom of the slope that draws cold winter air into talus at the base.  The rate of upslope movement (and therefore the intensity of the chimney effect cooling mechanism) is maximized when the outside air is coldest, especially at the top of the slope.  Such conditions are most likely to occur when there is no inversion layer, as occurs on the lee side of the Wind/Shellrock gap during the persistent, cold, continental air, east wind events of winter.

Note that while this explanation poses one possible explanation for the presence of apparent permafrost at the Wind/Shellrock gap, the theory is a little shaky, given that the strongest winter inversion layers are usually at about 1,500 feet, and therefore above the subject talus slope that spans 120-800 feet elevation.  Nevertheless, it may be possible that lower altitude inversions exist at certain times that slow air movement through talus during the critical cooling periods.  And again, the absence of such conditions west of the wind gap could accelerate upward flow, and therefore, the rate of cooling at the base of west Gorge talus slopes.

While this “inversion breakup explanation” may partially explain the strong cold talus mechanism at Shellrock, other factors could be involved too.  First, given the fact that clear skies are more likely west of the Wind/Shellrock gap during the coldest time of the year, it is likely that radiative cooling (i.e., infrared heat emission from the land surface into outer space during long winter nights), is most intense here.  Intensive radiative cooling occurs mainly on landscapes that lack infrared-blocking vegetation, fog or clouds.  Such clear atmospheric conditions are typical in the western Gorge during cold winter, high pressure weather systems.  Second, it could be possible that the wildly turbulent pressure patterns (and resultant winds) on the leeward (i.e., west) end of Shellrock are responsible for directly driving cold air into the base of the slope.  At the same time, these currents could be locally reducing pressures at the top of the slope, thus directly accelerating the flush of warm air from vents at the top and increasing the suction of cold air into the lower slope.

Third, the possible existence of ice-cored talus on the Oregon side of the western Gorge might be partially due to unique Gorge geology and topography, combined with a physical process known as the “Balch effect”.  The American explorer Edwin Swift Balch was perhaps the first scientist to note, inventory and explain the presence of localized, small periglacial ice features in Europe and America, including our own well-known Ice Cave some five miles WSW of Trout Lake, Washington.  Balch termed such features “Glacières”, or “freezing caverns” in his book published in 1900.  While Balch understood and described what is now termed the chimney effect, he recognized an even more basic mechanism that explains the formation of some underground ice features.  Balch effect cooling is driven simply by the fact that cold air, being denser than warm air, will flow downslope to fill low and contained openings in the landscape.  He found that such openings or pockets could include caves, mines, wells, porous talus fields, and rock fissures.  Balch theorized that such pockets could become perpetually frozen (i.e., decoupled from the upper air environment) by the seasonal flushing of warm air with cold air, persistence of the sunken cold and dense air mass, topographical shading, and the insulating behavior of the surrounding rock and air pockets.

For Balch effect cooling at western Columbia River Gorge talus fields to result in conditions something akin to the Trout Lake Ice Cave, it would be assumed that the talus at the base of such slopes would need to be topographically shaded, relatively deep, and contained in a closed topographic depression to prevent escape of cold air from the slope.  In the case of Shellrock Mountain, shading, volume and depth of talus at the mountain’s base is likely very high due to the mountain’s size and the talus proximity to the steep north cliffs.  There is additionally at least one geological mechanism that could have resulted in a bowl-like containment of the talus around the northern base of the mountain, that being the past deposition of landslide and/or alluvial debris from both the Oregon and Washington sides of the Columbia.  The possibility that such debris flowed across the Columbia River from the Washington side is not that remote, given the location of the Wind Mountain Landslide due north and oriented directly at the north side of Shellrock Mountain (see diagram below).  If such inundation of the relatively older talus slopes did occur from the north and west, it could have formed containment for cold air sinking into the lower talus margins, thus creating a Balch effect-caused permafrost environment.

Wind Mountain / Shellrock Mountain Wind Gap showing landslide

Finally, it is important to interject here that whatever cooling mechanism is dominant at Shellrock Mountain (chimney effect, Balch effect, etc.), a very cold source of air during the over-cooling period would be necessary to drive refrigeration at the base of the mountain.  As ventured in Chapter 5, this source is likely east wind events, though it is possible that cooling is being intensified by localized drainage of cold air from the north slopes of 4,960 foot Mt. Defiance, and other high western Gorge peaks overlooking the 20 mile-long “pika belt”.  Such downslope flows of intensely cold air would likely be occurring during the clear nights and morning that follow cloudy days.  Cloudy conditions during the preceding day would not allow much warming of the land surface prior to the cold night.

 

Ice Mountain:  The Course of Re-discovery — Chapter 6

A century ago, the frozen feature at Shellrock Mountain was probably just a local curiosity, though it did have real-world impacts on the construction and maintenance of the 1915 Columbia River Highway.  After the road was abandoned, the feature was mostly forgotten in absence of the old highway’s framework.  Today, however, it might assume several new and important contexts.  First, the feature is likely an important engineering and interpretive consideration with respect to the re-born Historic Columbia River Highway Trail.  Second, it has very important scientific study and interpretive values, especially if confirmed as anomalously low permafrost and periglacial ice for this elevation and latitude.  Third, its presence may have bearing on the future of a little understood species that is subject to changes in climate and alterations to its habitat.  While American pikas are far from being imperiled across their total North American range, most scientists would agree that they could be threatened along the fringes of this range. The Gorge’s unique low-elevation pikas would certainly be considered one such fringe population.

A Way Forward

The current day observation of the cold talus mechanism and possible permafrost at the base of Shellrock Mountain (and other talus slopes in the western Gorge’s 20 mile long “pika belt”) opens a wide variety of future geological, biological, meteorological, and climate-related study opportunities.

Foremost, is the opportunity for geological work to confirm and explain permafrost and periglacial ice at this nearly sea-level location.  Research of this type is increasing in places like the Alps due to the fact that so much human infrastructure is in close proximity to glacial and periglacial slopes that may become unstable during a warming climate.

Researchers interested in understanding cold talus and permafrost in talus slopes use three primary study techniques, including:   a) continuous temperature monitoring along slope profiles, b) boreholes designed to intercept subsurface ice for logging and long-term temperature monitoring, and c) geophysical investigations relying on the use of ground resistivity logging.  While the last two methods can definitely prove the existence of permafrost and ice, temperature monitoring along slope profiles is at least capable of illustrating the strength of the cold talus mechanism and the likelihood of frozen conditions.  This spring, I am hoping to begin monitoring slope profile temperatures in partnership with researcher Connie Millar of the USFS, and land managers including ODOT and USFS National Scenic Area office in Hood River.  Beyond that, it is hoped that others (perhaps Oregon Department of Geology and Mineral Industries, private industries, and universities) might have the ability to conduct the larger work of drilling boreholes, performing aerial thermal photogrammetry, and conducting geophysical surveys to find direct evidence of permafrost and periglacial ice.

Regardless of whether permafrost and ice is proven, the unique cold talus slopes of the western Gorge represent wonderful laboratories for the examination and interpretation of the anomalous, out-of-place biological features (fungi, mosses, vascular plants, amphibians, mammals, birds, etc.) that surround cold talus vents.  Perhaps most interesting would be a study intended to see whether Shellrock Mountain pika population are shifting closer to the base of cold talus slopes in response to climate-induced warming of their middle altitude ranges.   It has usually been assumed that pikas are only being driven to higher elevations in response to warming, but the inverse may also be true.  Unfortunately, those being forced downslope to the base of the Gorge’s cold talus slopes could one day be genetically isolated from the larger upper populations.  Taken to the extreme, if the cold talus cooling mechanism becomes less intense over time, the low elevation cold talus refuge could disappear altogether, which might spell the end of our unique low-elevation population.  Also interesting would be the study of whether pikas seasonally migrate up-and-down individual talus slopes to take advantage of optimal thermal conditions.  It may be possible that they shift downward toward the cool vent areas during the summer for heat shelter and food collection, and then shift upward toward warmer vent zones to survive the winter’s cold and wetness.

Next, there is the great opportunity to tie understanding of all these issues using a biogeographic approach, which would hopefully uncover the complex mix of atmospheric and geologic influences that account for intense cold talus, potential permafrost, and other habitat features at Shellrock Mountain and other locations in the western Gorge’s low elevation “pika belt”.  One interesting study would be a focus on the importance of talus rock type (including composition, size and shape) on pika habitat suitability in the Gorge.  Worldwide, talus slopes can be derived from most any bedrock type that occurs in the overlooking headwalls, but in the Gorge these are mainly limited to the two igneous rock types basalt and quartz diorite.  The twin intrusive volcanic necks of Shellrock Mountain and Wind Mountain are both composed of quartz diorite, which is somewhat lighter in weight and color than basalt.  Quartz diorite cliffs also tend to shed a more flattened and plate-shaped talus, which could have important implications on the size and shape of pika pocket openings, thermal insulation, sun shading, pocket roofing (water shedding character), and suitability for the dry storage of the pika’s “hay piles”.

Finally, as described in the fifth chapter, the topographic Wind/Shellrock wind gap is one of the most dominant meteorological features of the Gorge, and could account for the apparent over-cooling of talus slopes occurring in the western Gorge during winter.  Gaining complete understanding of the mechanism will be a significant job that involves installation of several meteorological monitoring sites around the wind gap, followed by fine-scale modelling of the turbulent wind directions, temperatures and pressure patterns.  As meteorologist Justin Sharp has ventured to say, conventional weather modelling techniques would not be able to unmask the complex air circulations and pressure patterns on the sides of Shellrock Mountain.  In his estimation, understanding would best rely on “computational fluid dynamics” (CFD) modelling to trace the likely air flows and talus heat transfers. CFD modelling, using the fastest of our supercomputers, is the tool that aeronautic engineers use to model complex airflows around aircraft and inside turbine engines.  Such methods are also used at the landscape scale by the wind power industry and others to understand flows surrounding wind turbines, buildings, bridges, etc., and associated topographic features.

 

Acknowledgments:

I thank Dr. Connie Millar of the US Forest Service and Dr. Justin Sharp of Sharply Focused LLC for their review, and for noting likely pitfalls contained in this very theoretical work.  I also thank Susan Hess (www.envirogorge.com) for editing suggestions.

Comments on this article can be posted below, or via email at stampfli@gorge.net.

 

About Steve Stampfli

Steve Stampfli was born and raised in Denver and the mountains of Colorado.  He obtained his bachelor’s degree in biology from Colorado College in 1975, and masters’ degree in environmental management from Duke University in 1979.  From there, he pursued interests in landscape restoration working as director of the Exploration and Mining Program for the state of South Dakota, and then as environmental coordinator for Wharf Resources Inc. Annie Creek Gold Mine in the Black Hills.  He moved to the Gorge in 1988, where he worked as manager of the Underwood Conservation District for fourteen years, and then five years as coordinator of the Hood River Watershed Group.  Since retirement he has continued working on various projects that relate to one of his main life interests, that being the reclamation and restoration of disturbed landscapes.